WASHINGTON -- John McCain is attacking as "dishonest and dishonorable" a new ad questioning John Kerry's heroism in Vietnam, but the White House is declining to condemn the ad.

The commercial, which is scheduled to be aired in several cities, features Vietnam veterans accusing the Democratic nominee of lying about his war record and betraying his comrades by opposing the conflict.

McCain said something similar was "pulled" on him when he ran against President George W. Bush in the 2000 primaries.

The Arizona GOP senator is a friend of Kerry's and also a decorated war hero.

"I deplore this kind of politics," McCain said. "I think the ad is dishonest and dishonorable. As it is, none of these individuals served on the boat (Kerry) commanded. Many of his crew have testified to his courage under fire. I think John Kerry served honorably in Vietnam. I think George Bush served honorably in the Texas Air National Guard during the Vietnam War."

Asked about the ad as the president flew to Ohio, Press Secretary Scott McClellan said Bush has never questioned Kerry's military service.

But McClellan did not denounce the specific ad.

He did note it is being aired by an ostensibly independent group and Kerry should join in calling for all such ads to be pulled.

Bush has been the object of lots of ads by what McClellen called "shadowy" groups.