With a shattering stroke from the sky, the United States appeared to have dealt a major setback to extremist forces by killing the charismatic leader of the Pakistani Taliban. Analysts said Baitullah Mehsud, believed to have been killed in a missile attack Wednesday while visiting his wife in a Pakistani tribal area, represented the top threat to Pakistan's stability. 'We've buried him more than once in the past. But assuming it is right, it is a pretty significant step. He became a symbol of the Taliban's war on the Pakistani state, much more than any other figure,' said Bruce Riedel, a former CIA officer and White House adviser. 'In the pantheon of terrorist leaders, I really have to say that (Al-Qaeda leader Osama) bin Laden and Ayman Zawahiri are the only other two that are higher than him,' said Bruce Hoffman, a terrorism expert at Georgetown University. According to The New York Times, the missile strike from a CIA drone took place as Mehsud, a diabetic, was on a drip infusion for his kidney ailment. Citing two unnamed Taliban fighters, the newspaper said Mehsud was being tended to at the time by one of his wives on the roof of a house belonging to his father-in-law, Mulvi Ikramuddin, in Zanghara village, in South Waziristan. Ikramuddins brother, a doctor, was treating him, the paper said. Pakistani officials say they are still awaiting physical proof of Mehsud's demise. Top militants of his Tehreek-e-Taliban (TTP) umbrella group were said to be gathering in their South Waziristan stronghold ahead of an 'important' announcement. Mehsud's elimination, which likely would have required close coordination between the Americans and Pakistanis, also indicated that the two often- mistrustful allies have cemented their security relationship, the analysts added. Mehsud was at the top of the Pakistani government's most wanted list, having been implicated in the 2007 assassination of prime minister Benazir Bhutto, whose husband is now president. He went on to lead a campaign of suicide bombings, assassinations and insurgent attacks that swept out of the border tribal areas into the Swat Valley, threatening Islamabad. Stopping him also had become a strategic goal for the United States, alarmed by deteriorating security conditions in nuclear-armed Pakistan and the safe haven provided to Al-Qaeda in Taliban-controlled border areas. 'He is also someone who has threatened to attack in the United States, London and elsewhere,' said Hoffman. 'Operatives of his movement have been arrested in the last eighteen months in Spain and the Netherlands. He was clearly moving toward a more international movement,' he told selfnews. It was unclear who would replace Mehsud, or the long-term impact on the movement. 'It will trigger a leadership crisis, they will find it very difficult to fill the vacuum. There cannot be a bigger loss for TTP than Mehsud,' a Pakistani expert on tribal affairs, Rahimullah Yusufzai, told selfnews. Possible successors include Hakimullah Mehsud, a militant commander; Wali Rehman, a favored spokesman; and Qari Hussain, the leader of a suicide bombing network, said Fredrick Kagan, a military expert. 'It's problematic whether they could fill the same shoes. Mehsud was well known and regarded in the ranks of the Taliban as a key leader,' said retired general Anthony Zinni, a former commander of US forces in the region. However, General Javed Ashraf Qazi, a former director general of the Inter- Services Intelligence of Pakistan, warned that the war against Islamic extremism was far from over. 'The rest of his group is still intact; the man who prepared the suicide bombers is still alive,' Qazi told The New York Times. 'Army action is still necessary to take them out.' The reported killing also throws a light on the US use of drones against human targets, a controversial tactic that critics say has too often resulted in civilian casualties, alienating Pakistanis. But Hoffman said: 'People who claim that the drones, either Reaper or Predator attacks, were ineffective are definitely going to have to reassess those claims in the wake of this attack.' Since US President Barack Obama took office, the pace of US attacks from unmanned aircraft inside Pakistan has increased despite tensions with Islamabad over civilian casualties. In May, CIA director Leon Panetta defended the tactic as precise, effective and 'very frankly, it's the only game in town in terms of confronting and trying to disrupt the Al-Qaeda leadership.' 