Obama urges immigration reform at July 4 citizen ceremony WASHINGTON (Reuters) - President Barack Obama used an Independence Day ceremony in which immigrants serving in the U.S. military became citizens on Wednesday to renew his election-year call for new immigration laws popular with an important part of his political base. Wearing a red tie to celebrate the July 4th holiday at the White House, Obama addressed about two dozen foreign-born military personnel who were taking advantage of a program that offers them citizenship in return for their service. Obama, who is running for re-election in November, seized the opportunity to talk up his recent order lifting the threat of deportation for hundreds of thousands of illegal immigrants who came to the United States as children. The move appealed to Hispanic voters, a major voting bloc that could swing the election to the Democratic incumbent in battleground states such as Nevada and Colorado. "What a perfect way to celebrate America's birthday - the world's oldest democracy - with some of our newest citizens," Obama told the group of military members and their families, who came from countries including Mexico, Ghana, the Philippines, Bolivia, Guatemala, China, and Russia. You put on the uniform of a country that was not yet fully your own. In a time of war, some of you deployed into harm's way. You displayed the values that we celebrate every Fourth of July - duty, responsibility, and patriotism," Obama said. Immigrants must come to the United States legally to enlist in the military. The issue of immigration has become a flash point in Obama's battle with Republican presidential candidate Mitt Romney to win the White House on November 6. Romney, the former governor of Massachusetts, has advocated a program of self-deportation for illegal immigrants, a proposal that has not gone over well with Hispanics. He accused Obama of being politically motivated with his move last month to give work permits to children of illegal immigrants, but he declined to say he would repeal the policy if elected. Obama holds a huge lead in polls over Romney among Latinos, though many are disappointed that he has not delivered on a promise to overhaul the U.S. immigration system. "Just as we remain a nation of laws, we have to remain a nation of immigrants," Obama said. That's why as another step forward we're lifting the shadow of deportation ... from deserving young people who were brought to this country as children. Obama's order, issued on June 15, circumvented Congress after it failed to pass legislation known as the DREAM Act, which would have helped address the issue of children who came to the country with their parents illegally and faced deportation. "It's why we still need a Dream Act: to keep talented young people who want to contribute to our society and serve our country," he said. It's why we need - why America's success demands - comprehensive immigration reform. U.S. Homeland Security Secretary Janet Napolitano, wearing a bright red blazer, administered the oath of allegiance to the men and women standing under glittering chandeliers in the White House East Room. Similar naturalization ceremonies for active-duty military personnel were held throughout the country. Back at the White House, the South Lawn was decked out in red-white-and-blue bunting and paper lanterns for an annual Fourth of July picnic honoring military service personnel and their families. Chefs grilled sizzling ears of corn ahead of the picnic. Editing by Jan Paschal