In an often tense 90-minute rhetorical battle, Bush accused Kerry of "naive and dangerous" views on North Korea and Iran, defended the March 2003 invasion to topple Saddam Hussein, and said his rival was as steady as a weathervane.

"I can see why people think that he changes position quite often, because he does," said Bush. "He said he thought Saddam Hussein was a grave threat, and now he said it was a mistake to remove Saddam Hussein from power."

Kerry hammered away at anemic job creation on Bush's watch and a report saying Saddam did not have the banned weapons that the president made the core of the case for war.

Asked by an audience member to answer Bush's charges he is "wishy-washy," Kerry said: "The president didn't find weapons of mass destruction in Iraq, so he's really turned his campaign into a weapon of mass deception."

"Let me tell you straight up: I've never changed my mind about Iraq. I do believe Saddam Hussein was a threat. I always believed he was a threat," Kerry said in response to increasingly fierce attacks from Bush's campaign.

Leading newspapers early Saturday described the debate as aggressive, with no clear winner. Analysts said Bush had rebounded from a poor performance in last week's debate, leaving the race deadlocked just over three weeks before voters go to the polls.

Two snap polls on who won showed a statistical tie. An ABC News poll and a CNN/USA Today/Gallup poll taken just after the match each gave Kerry a narrow win, but in both cases the difference between the two candidates was smaller than the margin of sampling error.

The two candidates roamed the floor of a university hall here as they took questions from an audience of 140 voters who said they were still up for grabs with less than a month before the November 2 election.

The president stayed on the offensive on national security and the economy as he worked to overcome a lackluster performance in their first debate last week.

After Kerry accused him of a "go alone" approach to Iraq, Bush angrily interrupted the moderator's efforts to ask a follow-up question, pointing to Britain, Italy, and Poland and saying "they're sacrificing with us" in Iraq.

Kerry countered that if US soldiers from Missouri serving in Iraq were from another country, that nation would have the third most troops there behind the United States and Britain, concluding: "That's not a grand coalition."

Bush charged the Democrat would be too worried about global opinion of the United States to make hard decisions like going to war, saying: "Sometimes in this world you make unpopular decisions because you think they're right."