Kerry argued that his 2004 rival should have pressured Iraqi leaders to set aside their differences and focus on making progress in assuming responsibility for security, a move that could lead to a reduction in U.S. troop levels.
"The absence of pressure I find is an enormous blunder that gives the Iraqi politicians a free pass to continue the status quo that most Americans understand is a failure, that's not working," Kerry said. "I'm amazed by it."
Kerry is a possible 2008 presidential candidate. He spoke to reporters after appearing at a campaign event with Iowa gubernatorial candidate Chet Culver.
The Massachusetts senator was responding to Bush's 15-minute telephone conversation Monday with the Iraqi prime minister. Bush called Prime Minister Nouri al-Maliki to quell rumors that the United States planned to set a deadline for Iraqis to assume security responsibilities. In his conversation, Bush said there was no deadline and that American troops would remain as long as they were needed.
Bush's comments can be compared to his "bring it on" challenge to terrorists, Kerry said.
"I think the president committed a gigantic blunder of the proportion of 'Bring it on,' " said Kerry. "When he has a conversation with the prime minister of Iraq and he climbs out and he says that he told him he doesn't have to worry, we're going to be there as long as it take, you've given a message that they can take as long as they want."
Kerry said even Republicans such as Sens. John Warner and Chuck Hagel are calling for a new strategy in Iraq, and Bush needs to get that message.
Danny Diaz, a spokesman for the Republican National Committee, said Kerry's comments "proves he will say and do anything to try to recapture his 15 minutes of fame."
"While President Bush and prime minister al-Maliki are committed to beating the terrorists in Iraq, John Kerry is devoted to convincing Iowans that he is somehow more capable of defending America this time around," Diaz said.