Kerry blasts Iraq invasion as 'historic' failure

But while calling for "a great national debate on Iraq" and the war on terror, Kerry broke new no ground on how he would handle the conflict. He repeated his hope to replace US troops with other international soldiers and Iraqi security forces.

Kerry made his scathing assessment in a speech prepared for delivery at New York University, pressing his latest tactic of focusing on Iraq and hammering Bush for misleading the US public about the deepening turmoil.

"The president claims it is the centerpiece of his war on terror," the Massachusetts senator said. "In fact, Iraq was a profound diversion from that war and the battle against our greatest enemy, Osama bin Laden and the terrorists."

"Invading Iraq has created a crisis of historic proportions and, if we do not change course, there is the prospect of a war with no end in sight," said Kerry, battling to unseat Bush in the November 2 election.

Kerry scored Bush over the president's acknowledgement that the administration had miscalculated the difficulties in restoring stability to Iraq after ousting Saddam Hussein in April 2003.

"That is one of the greatest understatements in recent American history," Kerry said. "His were not the equivalent of accounting errors. They were colossal failures of judgment and judgment is what we look for in a president."

Bush leads in polls on his ability to resolve the Iraq crisis and prosecute the war on terror and has scored points by accusing his rival of waffling, first voting to authorize the use of force and then opposing the war.