Ali won the world heavyweight title for the first time aged just 22, beating Sonny Liston in Miami 
 
 US President Barack Obama and boxing great George Foreman have led worldwide tributes to Muhammad Ali, who has died at the age of 74. 
 
 "Ali shook up the world - and the world is better for it," Obama said. 
 
 Foreman, who was beaten by Ali in the Rumble in the Jungle in 1974, said: "Muhammad Ali made you love him." 
 
 British Prime Minister David Cameron, musician Sir Paul McCartney, boxers Mike Tyson and Floyd Mayweather and golfer Tiger Woods also paid tribute. 
 
 Ali was admitted to a hospital in the US city of Phoenix, Arizona on Thursday suffering from a respiratory illness, a condition that was complicated by Parkinson's disease. 
 
 The three-time world champion died from septic shock caused by "unspecified natural causes", his spokesman Bob Gunnell said. 
 
 Ali's funeral will take place in his home town of Louisville, Kentucky at 19:00 BST on Friday, 10 June, where flags have been flying at half-mast since his death was announced. 
 
 Former US president Bill Clinton and comedian Billy Crystal will deliver eulogies at the service, which will be open to the public. A procession will also be held in Louisville on the same day. 
 
 'A wonderful, infectious, even innocent spirit' 
 
 Muhammad Ali attended Barack Obama's inauguration as president in January 2009 
 
 In a lengthy statement, Obama said both he and wife Michelle "pray that the greatest fighter of them all finally rests in peace". 
 
 "Like everyone else on the planet, Michelle and I mourn his passing," he said. "But we're also grateful to God for how fortunate we are to have known him, if just for a while; for how fortunate we all are that The Greatest chose to grace our time." 
 
 Ali's quick wit and vocal indignation over racial discrimination made him a compelling character away from the ring. He also refused to be drafted into the Army during the Vietnam War because of his religious beliefs, resulting in him losing his licence and world title. 
 
 "He stood with King and Mandela; stood up when it was hard; spoke out when others wouldn't. His fight outside the ring would cost him his title and his public standing," Obama added. 
 
 "It would earn him enemies on the left and the right, make him reviled, and nearly send him to jail. But Ali stood his ground. And his victory helped us get used to the America we recognise today. 
 
 "He wasn't perfect, of course. For all his magic in the ring, he could be careless with his words, and full of contradictions as his faith evolved. But his wonderful, infectious, even innocent spirit ultimately won him more fans than foes - maybe because in him, we hoped to see something of ourselves. 
 
 'Something greater than a boxer' 
 
 Ali and Foreman met in the famous Rumble in the Jungle on 29 October 1974 
 
 Speaking to BBC Radio 5 live, two-time world champion Foreman said: "Muhammad Ali was what I call beautiful. He has been something special. 
 
 "The man was the greatest. Forget about boxing, he was one of the greatest men to appear on television, in the media." 
 
 Foreman's loss to Ali in Kinshasa, Zaire [now DR Congo] 42 years ago stands as one of the most iconic moments in any sport. 
 
 Ali's 'rope-a-dope' strategy tired the unbeaten Foreman in the 80 degree heat, allowing him to force a stoppage in the eighth round. 
 
 "Little did I know I would be facing something greater than a boxer," Foreman said of the fight. 
 
 "He stood the test. He took everything I had and gave back worse. I loved the man. I wanted to beat him and knock him out but I loved the man." 
 
 'He stood for the world' 
 
 Don King, who promoted many of Ali's fights, including the Rumble in the Jungle, said: "It's a sad day for life. I loved Muhammad Ali, he was my friend. Ali will never die. 
 
 "Like Martin Luther King, his spirit will live on. He stood for the world." 
 
 Eight-weight world champion Manny Pacquiao described Ali as a "giant". 
 
 "Boxing benefitted from Muhammad Ali's talents but not as much as mankind benefitted from his humanity," the Filipino said. 
 
 Floyd Mayweather, a world champion across five divisions, added: "There will never be another Muhammad Ali. The black community all around the world, black people all around the world, needed him. He was the voice for us. He's the voice for me to be where I'm at today." 
 
 Listen: Muhammad Ali a 'complete inspiration' - Wladimir Klitschko 
 
 Boxing stars react on Twitter 
 
 Former undisputed world heavyweight champion Mike Tyson 
 
 Former WBC heavyweight champion Frank Bruno 
 
 Former WBA and IBF light-welterweight champion Amir Khan 
 
 'We were very lucky that he chose boxing' 
 
 Barry McGuigan, former world featherweight champion, said: "Everybody wanted to box because of him. He was just so amazing in every way. More than anything else, it was how humble and how brilliantly charismatic he was. 
 
 "He was a beautiful-looking man, a beautiful-looking individual and he had so much compassion. He was the greatest sportsman there has ever been and we were very lucky that he chose boxing." 
 
 World cruiserweight champion Tony Bellew described Ali as "the ultimate hero". 
 
 "It's heartbreaking news to wake up to. The greatest sportsman of all-time in my opinion. He transcended the sport and this is a sad day," he said. 
 
 "I hope something can be named after him. He can never be replicated." 
 
 Former world super-middleweight and light-heavyweight champion Joe Calzaghe said Ali was his "inspiration". 
 
 "People loved him, he was someone completely different, he backed it up in the ring and everybody wanted to tune in and watch him fight," the Welshman said. 
 
 "There'll never be another Muhammad Ali. He was a superstar." 
 
 Tributes flow in from beyond boxing 
 
 British journalist Michael Parkinson interviewed Muhammad Ali four times and remembers him as boxing's biggest ever star. 
 
 "He was a rockstar," Parkinson told BBC World Service. "It was not often I was gobsmacked but as he walked across the studio floor I'd never seen a more graceful or beautiful man, he was extraordinary. 
 
 "He was a man who could fell you with a blow - kill you maybe - yet he had beautiful hands with long tapering fingers." 
 
 Media playback is not supported on this device Muhammad Ali: "I wear one suit a day, I can only eat one meal a day, I can drive one car a day" 
 
 Former Beatle Sir Paul McCartney said "the world has lost a truly great man". 
 
 "Dear Muhammad Ali. I loved that man. He was great from the first day we met him in Miami, and on the numerous occasions when I ran into him over the years," McCartney said in a statement. 
 
 "Besides being the greatest boxer, he was a beautiful, gentle man with a great sense of humour who would often pull a pack of cards out of his pocket, no matter how posh the occasion, and do a card trick for you." 
 
 The Beatles met Ali at the boxer's training camp in Miami in 1964 
 
 British Prime Minister David Cameron said: "Muhammad Ali was not just a champion in the ring - he was a champion of civil rights, and a role model for so many people." 
 
 Former US President Bill Clinton said Ali possessed "a blend of beauty and grace, speed and strength that may never be matched again". 
 
 "We watched him grow from the brash self-confidence of youth and success into a manhood full of religious and political convictions that led him to make tough choices and live with the consequences," he added. 
 
 "Along the way we saw him courageous in the ring, inspiring to the young, compassionate to those in need, and strong and good-humoured in bearing the burden of his own health challenges." 
 
 The ANZ Stadium in Sydney displayed a tribute to Muhammad Ali before the international football friendly match between Australia and Greece on Saturday 
 
 Golfer Tiger Woods paid this tribute to Ali 
 
 Former Beatle Ringo Starr was among the thousands to pay tribute on social media ||||| The Greatest made the world a better place. His work is done. We are better for it. Thank you. RIP, Champ. # BePeacepic.twitter.com/VtPhYRJS3U ||||| Muhammad Ali’s death Friday brought his longtime friend and promoter Bob Arum to recall the former heavyweight champion as “the most transforming figure that I have encountered – for America and the world.” 
 
 Ali died at 74 in a Phoenix hospital, where he was moved this week for a respiratory illness, causing him to require life support Friday as family members came to his bedside. 
 
 He was diagnosed with Parkinson’s more than 30 years ago, moving many to tears with his arm-shaking lighting of the Olympic torch at the 1996 Summer Olympics in Atlanta, and family spokesman Bob Gunnell told NBC Friday, “We don’t have an official cause of death yet, but it has to be from complications of Parkinson’s.” 
 
 It was the three-time heavyweight champion’s dynamic personality and fighting that will be most remembered. 
 
 Veteran boxing publicist Bill Caplan worked on two Ali fights, including his famed 1974 “Rumble in the Jungle” in Zaire against then-unbeaten George Foreman. 
 
 “He was a great athlete, but the greatest publicity man I’ve ever known. He would do anything you asked [promotional-wise] and would think of a lot of himself,” Caplan said, recalling a scene months before the Foreman fight where the two heavyweights met casually inside an empty Hilton Hotel boardroom in Caracas, Venezuela. 
 
 A look at the life and career of boxing legend Muhammad Ali. 
 
 “I was like a fly on the wall for that,” Caplan said. “Ali was doing color on ABC with Howard Cosell. Ali couldn’t be any kinder one-on-one. He gave Foreman advice on how to handle being the champion, like he was a Dutch uncle -- couldn’t have been nicer. 
 
 “Then we walked outside, where there were a lot of people in the lobby and Ali said, ‘You see this robot [emulating Foreman’s slow-moving power punches]? You know what I’m going to do to him?’ 
 
 “You saw the two faces of Ali in one second. George was laughing and laughing. He got it.” 
 
 After Ali beat Sonny Liston for the heavyweight belt, he faced being drafted to the Vietnam War, and refused – provoking a three-plus-year absence from the ring and serving as a lightning rod during the height of the civil rights era. 
 
 “It’s hard for people 50 or younger to realize what this country was like in the 1950s and ‘60s, how bad it was for African-Americans in this country – how they fought just to eat at a lunch counter or stay at a hotel,” Arum said. “There was no opportunity. 
 
 “Ali spoke out against that in a way that really connected with people, even more than the melodic and philosophical way that Martin Luther King Jr. spoke out. Because Ali was a great sportsman and boxer, he was able to reach people and, I think, had a tremendous effect on bringing change to this country.” 
 
 No act was more principled than giving up massive boxing purses to defy the draft, Arum said. 
 
 “Once people saw that he sacrificed his livelihood for what he believed in, that really elevated him in the minds of people to be almost saint-like,” Arum said. “Everybody, myself included, counseled him not to take that step that led him to not fight for three and a half years, but he felt he was doing the right thing. And it ended up that it was the right thing – for him, the world and the country.” 
 
 Ali proceeded to return to the ring against Joe Frazier in an epic 1971 showdown, then recaptured the heavyweight belt by knocking out Foreman in 1974 in Africa. Ali quickly avenged a 1978 loss to Leon Spinks for the third union with the belt. 
 
 “His story and his character and his life will be part of history that will be studied by whoever looks back on the last 50 years,” said Arum, who promoted 26 Ali bouts, including the 1975 trilogy capping “Thrilla in Manila” fight with Frazier that is seen as the beginning of the brain damage that plagued his later life. 
 
 Foreman remembers learning a few lessons inside and outside the ring from Ali. 
 
 "Back in the time that Joe Frazier, Ali and I were going strong, they called us all great fighters. There's no question the greatest of all was Muhammad Ali," Foreman said Friday night. "I never had any animosity toward him. Never. I always respected him and I learned from him." 
 
 Foreman said what he learned most was how to get along with reporters and to be more clever in the ring -- an asset that allowed Foreman to recapture a heavyweight belt 20 years after the "Rumble in the Jungle." 
 
 Oscar De La Hoya, who fought in front of Ali sitting ringside in the first bout at Staples Center in 2000, said in a prepared statement, "Muhammad Ali is ... the fighter who ushered in the golden era of boxing and put the sport on the map. He paved the way for professional fighters including myself, elevating boxing to become a sport watched in millions of households around the world. 
 
 "Ali's talent was undeniable ... beyond his incredible talent, he also made boxing interesting. Ali was fearless in the ring, and took on the toughest, most challenging opponents. Ali exemplified courage -- he never took the easy route, something to be admired in and outside of the ring. 
 
 "Let us remember a man who pursued greatness in everything he did and be inspired to hold ourselves to that same standard. Rest in peace, my friend." 
 
 Former champion boxer Manny Pacquiao weighed in from the Philippines. 
 
 “We lost a giant today,” said Pacquiao, who was inspired by Ali’s devotion to the public and was recently elected to a Senate seat in his country. “Boxing benefited from Muhammad Ali's talents, but not nearly as much as mankind benefited from his humanity. Our hearts and prayers go out to the Ali family. May God bless them.” 
 
 Arum witnessed Ali’s standing as the most well-known person in the world when he accompanied the then-retired icon to China to promote a boxing show in the early 1990s, after the country banned the sport during Ali’s reign. 
 
 “Going through customs, there were these massive groups of Chinese that recognized him and went crazy. I was stunned,” Arum said. “He was a magical person and obviously the most amazing person I’ve had the privilege of being around in my lifetime.” 
 
 Lance.pugmire@latimes.com 
 
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– Muhammad Ali died Friday at the age of 74, likely from complications related to Parkinson's disease. The death of the Greatest led to an outpouring of tributes and memorials from those who knew him and others who admired him from afar. Here are 13 of those reactions from athletes, celebrities, and politicians: “It's been said it was Rope a dope, Ali beat me with no his beauty that beat me. Most beauty I've know loved him," George Foreman tweeted. “Thinking of #MuhammadAli and remembering a man who was not afraid to take a stand and who was committed to being his authentic self," Billie Jean King tweeted. "Ali shook up the world—and the world is better for it," the BBC quotes President Obama as saying in a statement. “The greatest man I have ever known," Billy Crystal tweeted. “The Greatest made the world a better place. His work is done. We are better for it," Carl Weathers tweeted. "Ali exemplified courage—he never took the easy route, something to be admired in and outside of the ring," the Los Angeles Times quotes Oscar De La Hoya as saying. “Boxing benefited from Muhammad Ali's talents, but not nearly as much as mankind benefited from his humanity," the Times quotes Manny Pacquiao as saying. “His may be the Greatest of 20th century American stories," Neil deGrasse Tyson tweeted. “We will NEVER forget your courage, standing up to those in power. You gave up your title & your career rather than kill Vietnamese," Michael Moore tweeted. "From the day he claimed the Olympic gold medal in 1960, boxing fans across the world knew they were seeing a blend of beauty and grace, speed and strength that may never be matched again," ABC News quotes a statement from Bill and Hillary Clinton as saying. “Muhammad Ali was the greatest, not only an extraordinary athlete but a man of great courage and humanity," ABC quotes Bernie Sanders as saying in a statement. “Muhammad Ali is dead at 74! A truly great champion and a wonderful guy. He will be missed by all!” Donald Trump tweeted. “God came for his champion. So long great one," Mike Tyson tweeted. (Click here for the best quotes from Ali himself.)