Mr John Kerry and President Bush have clashed again over Iraq and national security as their bitter race for the White House raced towards an increasingly tight finish.
Mr Kerry, has charged that George W. Bush's "failures" had left the United States more exposed to terrorism, while Mr Bush condemned his challenger for failing to see the "true dangers" in a post-September 11th world.
Ahead of the November 2nd ballot, polls showed the candidates running even nationally, but Mr Kerry edging up in several critical states that could decide the presidency.
On a day when he travelled through three key states - Iowa, Pennsylvania and Ohio - the Massachusetts Democrat accused Mr Bush of showing "contempt" for US allies, and of embarking on a "profound diversion" from the anti-terror fight in Iraq.
"On George Bush's watch, America is more threatened than we were before," Mr Kerry said in a speech in Waterloo, Iowa.
"The president's failures in Iraq have made us weaker, not stronger in the war on terrorism. That is the hard truth. The president refuses to acknowledge it," Mr Kerry said, arguing Mr Bush had proven himself unfit to lead the world.
"This president says he is a leader. Well Mr president, look behind you, there's hardly anyone there. It's not leadership if we haven't built the strongest alliance possible and America is going almost alone."
Mr Bush, campaigning in Mason City in the same state, seized on Kerry's comments in a New York Timesinterview this month that the September 11 strikes "didn't change me much at all.
"The next commander in chief must lead us to victory in this war, and you cannot win a war when you don't believe you're fighting one."
"You cannot lead our nation to decisive victory on which the security of every American family depends if you do not see the true dangers of a post-September the 11th world," Mr Bush said.
Mr Kerry's campaign was boosted by news that Democratic party talisman, ex-president Bill Clinton will join him at a rally in Philadelphia next Monday.
There was a worrying sign for Mr Bush as a new poll showed his approval rating in the fight against terrorism dropped below 50 per cent this month for the first time since the September 11th, 2001 attacks.