"Faced with unrelenting attacks on his military record, Sen. John F. Kerry on Thursday said a Republican-funded group of veterans is lying about his service in Vietnam and operating as a front organization for President Bush.

The president 'wants them to do his dirty work,' Kerry said.

Under pressure from Democrats to respond to a television ad and book challenging his valor in Vietnam, Kerry, for the first time, lashed out at Swift Boat Veterans for Truth and the president, accusing them of conspiring to smear his decorated military record, and released a new ad highlighting his heroism in combat.

'More than 30 years ago, I learned an important lesson. When you're under attack, the best thing to do is turn your boat into the attack,' Kerry told a few thousand union supporters here. 'Thirty years ago, official Navy reports documented my service in Vietnam and awarded me the Silver Star, the Bronze Star and three Purple Hearts. Thirty years ago, this was the plain truth. It still is. And I still carry the shrapnel in my leg from a wound in Vietnam.'

Kerry, who has made his military service a centerpiece of his candidacy, was forced to defend his war honors as the attacks on his integrity came to dominate the campaign. Aides said Kerry has been flooded with calls from concerned veterans, and a CBS poll released last night showed the senator from Massachusetts losing significant support among those who served in the military.

While Kerry struck back at the group, he did not address some of the accusations, including the charge that he lied about crossing into Cambodia on Christmas Eve 1968. Kerry, in a statement, maintains he was in Cambodia while serving in Vietnam but does not state that it was on that date. Swift Boat Veterans for Truth has also accused Kerry of lying about his war record to win a Bronze Star and of using a self-inflicted wound to claim a Purple Heart, charges the Democratic nominee denies.

On its Web site, the veterans group says that the wound that led to the first of Kerry's three Purple Hearts was minor and self-inflicted, thus ineligible for the award. Kerry, through a spokesman, said the wound was not self-inflicted.

The Washington Post cited military records Thursday that support Kerry's account on the Bronze Star citation.

Instead of rebutting each charge, Kerry blamed Bush for sanctioning such highly personal attacks.

'Of course, the president keeps telling people he would never question my service to our country. Instead, he watches as a Republican-funded attack group does just that,' Kerry told the International Association of Fire Fighters meeting here. 'Well, if he wants to have a debate about our service in Vietnam, here is my answer: Bring it on.'

Drew Whitlow and Bill Zaladonis, former naval officers who served under Kerry's command, came to the event to defend the senator's record.

Bush has refused to condemn the ad, and there is no evidence the president's campaign has direct connections to the anti-Kerry veterans group.

Kerry spokeswoman Stephanie Cutter said he made the decision late Wednesday to fight back, during a teleconference from his Boston home with traveling staff and advisers in Washington. 'When you shed your blood for your country, your instinct is to fight back,' she said.

Swift Boat Veterans for Truth, which is funded in large part by Bob Perry, a Texas Republican, has knocked the Democratic nominee's campaign off stride with a small but effective advertising buy in the battleground states of Ohio, West Virginia and Wisconsin. The group spent about $500,000 on the ad, but its allegations that Kerry exaggerated his combat record to win medals have been on the Internet, the 24-hour cable channels and, most recently, the nation's major television networks and newspapers.

During the week ending Aug. 8, 966,000 people visited the anti-Kerry group's Web site, 34,000 fewer than those who visited Kerry's official site, according to Nielsen/Net Ratings. The new CBS poll found Kerry winning 37 percent of veterans' votes to Bush's 55 percent. (The two were tied at 46 percent after last month's Democratic National Convention, where Kerry highlighted his service.)

'They have been very effective at using the August lull to drive a story' in news outlets, said Rep. Rahm Emanuel (D-Ill.). Kerry, who planned to conserve resources by not buying television ads this month, will spend at least $180,000 to respond, his aides said.

Several Democrats said Kerry waited too long to condemn an ad designed to undermine the cornerstone of his political career and the overriding theme of the convention that nominated him for president: his heroics in war.

'If it were me, I would have come out a lot earlier,' said Steve Jarding, a Democratic strategist. 'Attack ads on people's character work. It's a sad fact of American politics.' Jarding, who advised Sen. Bob Graham (Fla.) during the presidential primaries, said Kerry is especially vulnerable to misleading attacks because most voters still do not know much about him. 'When someone levels a negative attack, particularly when it goes to your character, you have to respond' immediately, he said.

Cutter said the campaign relied on the news media, surrogates and 700 letters to the editor to discredit the charges. 'But every time one of these guys [from the Swift boat group] shows up on Fox, we get calls from veterans,' she said.

Kerry plans to bring in two seasoned communication specialists to help defend him from attacks, aides said: Joe Lockhart, White House spokesman under President Bill Clinton, and Joel Johnson, a lobbyist who also worked for Clinton.

Emanuel said Kerry has an opportunity to 'turn this and backfire it on the White House,' which is what the Democratic nominee began trying with his remarks Thursday. The campaign wants to convince voters that Bush and White House political director Karl Rove are behind the effort, at least in spirit.

Perry, a Houston home builder, initially contributed $100,000 to Swift Boat Veterans for Truth and recently gave another $100,000. Perry has given millions of dollars to GOP efforts over the years, including $46,000 to Bush's gubernatorial campaigns in 1994 and 1998. He gave $2,000 to Bush's reelection campaign this year, records show. Seven of the 10 initial financial contributors to the veterans group have given to Bush's campaign this year, according to PoliticalMoneyLine.

Yet many of the veterans affiliated with the anti-Kerry effort do not have obvious relationships with the Bush campaign, nor do some of its donors.

Tad Devine, a top Kerry strategist, said Bush's refusal to condemn the content of the ad suggests an alliance. If Bush had, 'that would have changed the whole chemistry of this debate,' he said. Sen. John McCain (R-Ariz.), a Bush supporter, has joined Kerry in calling on the president to repudiate the content of the ad, but Bush has refused. Instead, Bush and his spokesmen have condemned all groups financed by unlimited 'soft money' and called on Kerry to do the same. 'The president thinks that we should get rid of all of this unregulated soft-money activity by these shadowy groups,' White House spokesman Scott McClellan said Thursday.

GOP strategists said Bush's refusal to condemn the ad is smart because doing so would undermine what appears to be an effective hit on his challenger.

The dispute is unlikely to end soon. John O'Neill, a member of Swift Boat Veterans for Truth and author of the anti-Kerry book 'Unfit for Command,' said the group raised nearly $500,000 from 10,000 donors in recent days.

The group is planning to air a new ad starting Friday, though it is unclear what it will say. Group officials who discussed strategy on the condition of anonymity said the anti-Kerry group plans to hammer the Democrat for his war claims and his war protests after he left Vietnam, especially his claim that U.S. soldiers committed war crimes. The veterans, 15 or so who participate in conference calls most mornings at 7 to plot strategy, are also arranging local veterans to criticize Kerry when he visits their states, O'Neill said.

In its current TV ad, a Swift boat veteran says, 'John Kerry lied to get his Bronze Star. . . . I know, I was there, I saw what happened' -- a reference to the mission on March 13, 1969, when Kerry pulled Lt. Jim Rassmann from a river after an explosion knocked Rassmann off Kerry's boat. The ad says Kerry was not under fire. That episode is also a focus of O'Neill's book.

But The Post reported Thursday that the military records of Larry Thurlow, one of Kerry's accusers, show that Kerry's boat faced fire when he pulled Rassmann from the water.

The new 30-second Kerry ad says the Navy documented Kerry's 'heroism and awarded him the Bronze Star.' In the ad, Rassmann says: 'All these Viet Cong were shooting at me. I expected I'd be shot. When he pulled me out of the river, he risked his life to save mine.'" (Lois Romano and Jim VandeHei, Washington Post, August 20, 2004)