Democrat Mr John Kerry has made his sharpest assault yet on President George W. Bush's strategy in Iraq.
In his New York speech, Mr Kerry condemned Mr Bush for failing to tell the truth about Iraq and making a series of "catastrophic" decisions that he said turned Baghdad into a haven for terrorists and made the United States less secure.
"In Iraq, this administration has consistently over-promised and under-performed," the Massachusetts senator told supporters at New York University.
"This policy has been plagued by a lack of planning, an absence of candor, arrogance and outright incompetence."
Mr Kerry's comments drew a sharp response from Mr Bush, who said Mr Kerry "prefers the stability of a dictatorship to the hope and security of democracy" and accused him of adopting Mr Bush's own proposals on what to do next in war-ravaged Iraq.
"Today my opponent continued his pattern of twisting in the wind with new contradictions of old positions on Iraq," Mr Bush said in Derry, New Hampshire.
The tough exchange came amid increasing violence in Iraq and fresh doubts about Baghdad's path to democracy and whether January's national elections can be held as scheduled.
Mr Bush heads to New York today to face critics at the United Nations and will meet Iraqi Prime Minister Mr Iyad Allawi on Thursday at the White House .
Campaign officials have agreed on three televised presidential debates between Mr Bush and Mr Kerry that will begin next week in Florida as the race for the White House heads into a final six-week dash.
CBS News, in an embarrassing reversal, admitted it was misled over the authenticity of documents it aired in a story challenging Mr Bush's Vietnam-era National Guard service and said it was "a mistake" to air them without authentication.