Sen. John F. Kerry on Monday accused President Bush of deception in taking the country to war in Iraq and historic miscalculations since the invasion ended, arguing that Saddam Hussein posed no imminent threat and that his removal has turned Iraq into a terrorist breeding ground that has left the United States even less secure.

In his most comprehensive and stinging indictment of the administration, Kerry charged that by nearly every measure, from attacks on U.S. forces to the pace of reconstruction to the training of an Iraqi security force, conditions in Iraq are far worse than the president has acknowledged. Kerry called the November election a choice between staying the course with failed policies and a change in direction that he said is urgently needed to prevent disaster in Iraq.

"The president misled, miscalculated and mismanaged every aspect of this undertaking and he has made the achievement of our objective -- a stable Iraq, secure within its borders, with a representative government -- far harder to achieve than it ever should have been," Kerry said in a speech at New York University.

Bush and Vice President Cheney immediately attacked Kerry for repeatedly changing his position. "He's saying he prefers the stability of a dictatorship to the hope and security of democracy," Bush said in New Hampshire. "I couldn't disagree more and not so long ago, so did my opponent."

Kerry's speech came one day before the president is scheduled to address the United Nations. Bush aides said he would use his U.N. speech to say that Iraq is making progress toward stability and democracy, despite signs that the insurgency there has gained strength. On Thursday, Bush will host Iraqi Prime Minister Ayad Allawi at the White House. Officials predicted Allawi would offer an assessment that will rebut what they called Kerry's grim description of conditions in Iraq.

Kerry told his audience that, if elected, his goal would be to withdraw all U.S. forces within four years, beginning sometime next summer. But he warned that unless Bush begins to act this week at the United Nations, the prospects of being able to meet that timetable could be compromised.

Bush, he said, should lobby other nations this week to make good on their pledges for more military and financial support contained in a U.N. resolution approved last spring. "Not a single country has answered that call, and the president acts as if it doesn't matter," he said, noting that of $13 billion pledged, just $1.2 billion has been delivered.

Kerry said that the administration has inflated its estimates of how quickly Iraqi security forces are being trained and that Bush should immediately expand training programs, both inside and outside Iraq. On reconstruction, the Democratic nominee said that the administration has spent just $1 billion of $18 billion authorized by Congress and that Bush should revamp the reconstruction process by inviting in more Iraqi firms rather than large U.S. corporations such as Halliburton.

Kerry also said the administration must act quickly to assure that elections scheduled for next year can be held, beginning with the recruitment of an international security force to help protect any U.N. team that is sent there to facilitate those elections.

White House communications director Dan Bartlett said Kerry's prescription echoes what Bush already is trying to do in Iraq.

Kerry used his 45-minute address, which was interrupted frequently by applause, to challenge the president's veracity and credibility -- and to counter criticism that he not only has shifted positions repeatedly on Iraq but also has failed to stake out clear differences with Bush on the road ahead.

Advisers said Monday's speech would form the backbone of the case Kerry will make against the president as the two candidates prepare for their first debate Sept. 30 in Miami. Kerry's goal is to get off the defensive on Iraq and persuade voters that, if Iraq is the frontline in the war on terrorism, as Bush says, then the president's overall foreign policy leadership should be judged a failure.

In condemning the administration, Kerry went further than he has in the past to dispute Bush's principal rationale for going to war -- that Hussein's quest for weapons of mass destruction required a preemptive strike. He also sought to make clear that he would not have gone to war, even as he again defended his October 2002 vote for the congressional resolution authorizing Bush to do so. Kerry said that three dozen nations had greater capacity to develop nuclear weapons than Iraq.

"Saddam Hussein was a brutal dictator who deserves his own special place in hell," Kerry said. "But that was not -- that was not -- in itself a reason to go to war. The satisfaction that we take in his downfall does not hide this fact: We have traded a dictator for a chaos that has left America less secure."

To Bush's argument, made repeatedly on the campaign trail, that despite the failure to find weapons of mass destruction he would do the same thing now as he did in the spring of 2003, Kerry said: "How can he possibly be serious? Is he really saying to America that if we know there was no imminent threat, no weapons of mass destruction, no ties to al Qaeda, the United States should have invaded Iraq? My answer: resoundingly no. Because a commander in chief's first responsibility is to make a wise and responsible decision to keep America safe."

Officials in the Bush-Cheney campaign immediately responded that Kerry had again changed his position. They cited the senator's words during the Democratic primaries, when he criticized former Vermont governor Howard Dean for saying that the Iraqi leader's capture did not make the United States safer, arguing those who believed that did not have the judgment to be president.

Bartlett challenged Kerry's portrayal of conditions in Iraq and said his timing, just as Allawi is arriving in the United States, sent the wrong signal to those working to stabilize Iraq. "To disparage everything being done by casting everything in the negative light is not what I think the American people are looking for," he said.

Kerry charged that Bush repeatedly failed to tell the truth before the war, on everything from the threat posed by Hussein to what it would take militarily and financially to prevail after the invasion. He said Vice President Cheney remains one of the few holdouts. "Only Vice President Cheney still insists that the Earth is flat," he said.

Kerry argued that Bush's failure to tell the truth before the war has been topped by repeated miscalculations since then. "His miscalculations were not the equivalent of accounting errors," he said. "They were colossal failures of judgment -- and judgment is what we look for in a president."

Kerry's running mate, Sen. John Edwards (N.C.), joined in the criticism, saying at a town hall meeting in Raleigh, N.C., that the president has been "completely incompetent" in administering the war and that Bush's actions have been "a disaster." He added, "The only two people in America who wouldn't change what they've done in Iraq are George W. Bush and Dick Cheney."

During a question-and-answer session, Edwards was asked about his vote for the Iraq resolution by a young man who said he was a Marine Corps reservist and a Democrat. "Why are my friends dying over there?" the man asked. "Why did you vote for that?"

"I stand by my vote on the resolution," Edwards said. "But I did not give George Bush the authority to make the mess he's made in Iraq."

Staff writer David Snyder, traveling with Edwards, contributed to this report.