NEW YORK (Reuters) - Around 200 U.S. Army veterans and Vietnamese people demonstrated outside Democratic presidential front-runner John Kerry (news - web sites)'s New York headquarters on Saturday to protest his opposition decades ago to the Vietnam War.

Waving American and South Vietnamese flags and singing the U.S. national anthem, they held up signs saying "Hanoi John," and "Kerry Betrayed Vietnam Vets."

"We won't sit by and let the American people think that we are going to stand by somebody who stabbed us in the back," said Jerry Kiley, a veteran and one of the protest organizers.

Kerry, a Massachusetts senator and probable presidential challenger to President Bush (news - web sites) in November, became a leader of the anti-war movement after returning from Vietnam, where he was decorated with a Silver Star, a Bronze Star and three Purple Hearts.

"John Kerry served his country honorably," said Mark Kornblau, New York spokesman for Kerry's campaign. "This protest is being organized by an individual who has made a career of profiting from tragedy."

Questions about Kerry's anti-war activities arose after some Democrats made an issue of Bush's service in the domestic Air National Guard, questioning whether he showed up for duty in Alabama in the early 1970s.