HUNTINGTON, W.Va. — Democratic presidential candidate John Kerry promised to be a "veteran's veteran" Tuesday as the White House tried to sour his support among a key constituency by airing a commercial accusing him of rejecting funding for soldiers at war in Iraq.

Kerry warned an audience of veterans that President Bush has misled the country on everything from the war to the economy and had broken promises to veterans needing health care. From the Oval Office on Tuesday, Bush questioned Kerry's own truthfulness by calling for him to identify the world leaders Kerry has said would rather see him as president.

The Massachusetts Democrat later went to Charleston to accept his near-uncontested win in the Illinois primary, which his campaign says gives him the delegates needed to mathematically clinch the nomination. Kerry will claim that prize at the Democratic convention in Boston this summer.

He thanked Illinois voters "for helping us achieve our goal — a nomination marked by unity and not division."

"Together, in the months ahead, we will call on the best in Americans — and stand up for the best in America," Kerry told about several thousand cheering backers. "I say to you tonight: A new day is on the way."

The primary win was one bright spot during a series of tough days for Kerry. He came under a choreographed assault from Republicans from Bush on down after refusing to name the world leaders he says privately support his campaign. At the same time, Bush launched negative campaign ads that seek to define Kerry in harsh terms for the many voters to whom he is still unfamiliar. Both moves have made it difficult for Kerry to get his message out to voters.

In his first visit to West Virginia since becoming the presumptive nominee, Kerry tried to define himself as a war hero. The state, with 203,000 veterans, or 15.4 percent of its adult population, is home to more veterans per capita than all but Alaska, Montana, Nevada and Wyoming. Although solidly Democratic in past elections, West Virginia sided with Bush instead of Al Gore in 2000. Its five electoral votes would be essential in another close election.

"Nothing is more important than telling the American people the truth about the economy, health care, and war and peace," Kerry told veterans in Huntington. "This administration has yet to level with the American people."

In a nod to Mountain State geography, Kerry said, "On issue after issue, this president's misleading misstatements have produced a credibility gap as big as the New River Gorge."

Although Kerry has said he won't break confidences by naming any of the overseas leaders, Bush told reporters, "If you're going to make an accusation in the course of a presidential campaign, you ought to back it up with facts."