Howard Dean has brought an end to the polite public tone of the Democratic presidential primary by singling out John Kerry's position on Iraq.

Kerry, a senator from Massachusetts, and Dean, former governor of Vermont, are virtually tied for the lead among nine Democrats in a recent poll of New Hampshire voters.

Dean has gained support among anti-war voters for his opposition to the invasion of Iraq and in recent days has ramped up his criticism that Kerry's stance has been unclear.

"To this day I don't know what John Kerry's position is," Dean said Thursday in a speech to Iowa activists. "If you agree with the war, then say so. If you don't agree with the war, then say so, but don't try to wobble around in between."

Kerry has said he will not respond to Dean. His spokesman Robert Gibbs would not comment either, other than to say, "Democrats are disappointed that Howard Dean has decided to use a war for political gain and attack other candidates in a negative, divisive and personal way."

Kerry has long said Saddam Hussein must be disarmed and removed from power, and he voted to give President Bush the authority to strike Iraq. But he has strongly criticized Bush for his actions leading to the war, saying he should have given diplomacy more time and his failure to do so has alienated America's allies.

Chicago-based Democratic analyst David Axelrod said Dean has deftly handled his Iraq position to emerge as a threat to Kerry in Iowa and New Hampshire, which hold the first primary nominating contests.

"They both are competing for progressive, more educated voters who tend to be more anti-war," he said. "I think on many measures, Kerry would be an attractive candidate to those folks, but the war could be a problem for him and Dean has taken advantage of that."

Dean has won cheers from Democratic audiences by saying he would not have voted for the war resolution his congressional rivals helped pass, saying it is "the wrong war at the wrong time." But he has said he would support military action if it was proved Iraq had nuclear weapons and refused to disarm within 60 days.

Axelrod said Dean has not always been clear about his own position, pointing to his refusal to say whether the troops should be pulled out of Iraq at a Wednesday night appearance in Boston. Last week, Dean told reporters in Washington the troops must stay and finish the fight now that they are on the ground.

"He's criticizing Kerry for his inconsistency, but he could get hoisted on his own petard," Axelrod said.

A Democratic nominee who criticizes the war during the primary could have trouble appealing to moderate and conservative voters in the general election against Bush, said University of Vermont political science professor Garrison Nelson.

"The war doesn't cause any ambiguity among Republicans, but this is a battle among Democrats," Nelson said. "And it will get nastier before it gets nicer."