Democratic challenger John F. Kerry plans an aggressive attack on President Bush and his policies in Iraq, seeking to put the president on the defensive over an issue that has plagued Kerry's candidacy for months.

Bush has tried to emphasize Iraq's progress toward democracy, but events there have undermined that message in a week that has included car bombs, kidnappings and more U.S. casualties. Kerry advisers said they have concluded that they must engage directly on the issue of Iraq, despite their hopes of shifting attention to the economy, health care and other domestic issues, and say that renewed concerns among the American public about the situation in Iraq provide a fresh opening to challenge Bush more directly.

Kerry began the attack Thursday, charging that Bush continues to mislead the country on Iraq, and will escalate that criticism in the coming week. "He has led us into a situation that is more dangerous and destabilizing with each passing day, whether the president is willing to admit that or not," said Kerry senior adviser Joe Lockhart.

With some Kerry advisers convinced he cannot win a debate over whether the United States should have gone to war, given Bush's relentless attacks on Kerry for shifting his positions on the war, the Massachusetts senator has settled on a two-phase plan to refocus the debate. Aides say he will first challenge the president's optimistic assessment of conditions in Iraq and then draw a sharp contrast with Bush over getting the United States out of the country within four years.

The president's advisers say Bush maintains the public's confidence on Iraq and the war on terrorism, in large part because they say Kerry has yet to provide a clear explanation of why he voted to authorize the war in the fall of 2002 but later opposed $87 billion for Iraq and Afghanistan. Kerry has been urged by some advisers to say his initial vote was wrong, given what Bush did with that authority, but he has resisted.

White House communications director Dan Bartlett said that when the public compares Bush and Kerry on Iraq, they consistently put their faith in the president. As such, Bartlett said, the White House welcomes any attacks Kerry plans to launch. "We believe each day that we're debating the war and debating Iraq, it's an advantage to us," he said.

Iraq has shaped the presidential debate through the year and will assume center stage again this week, with Bush addressing the United Nations on Tuesday and welcoming Iraqi Prime Minister Ayad Allawi at the White House on Thursday. Kerry will be in New York on Monday and Tuesday, and advisers were working this weekend on plans for a retooled message that will accuse Bush of failure since the initial invasion of Iraq ended in the spring of 2003.

Bartlett said Bush would use his U.N. speech to deliver "a very passionate case about the need for democracy to take root in a very troubled part of the world" and use the Allawi visit Thursday to highlight the new leadership in Iraq. "He will talk about the fact that at difficult moments, this is one where it's all the more important for us to keep our resolve," Bartlett added.

The president's strategy of emphasizing progress toward stability and democratic elections early next year hit a wall last week, not only because of increased violence in Iraq, but also from reports of a classified July national intelligence estimate that painted a gloomy picture of the long-term outlook in Iraq. In addition, the administration came under fire from senior Democratic and Republican senators on the Foreign Relations Committee.

Bush used his radio address yesterday to argue that his policies are working and to address concerns about Iraq and Afghanistan, warning that violence is likely to increase in both countries as elections near. "Terrorist enemies are trying to stop the progress of both those countries, and their violent, merciless attacks may increase as elections draw near," he said.

Bush's effort will come at a moment when there is plenty of dissonance that threatens to undercut his message. A car bomb that exploded Saturday in Kirkuk, killing at least 20 people, was the latest attack to underscore the challenges facing U.S. forces in their effort to stabilize the country. The classified national intelligence estimate revealed last week said a worst-case scenario would have Iraq plunged into civil war, with hopes for stability tenuous under the most optimistic scenario, leading Kerry to charge that Bush lives in "a fantasy world of spin" in his descriptions of progress in Iraq.

Two Republicans on the Senate Foreign Relations Committee, Richard G. Lugar (Ind.) and Chuck Hagel (Neb.), added their voices to those critical of the administration. Lugar assailed the "dancing-in-the-street crowd" within the administration for offering misleading predictions of progress on reconstruction. Hagel said the United States is "in a lot of trouble" in Iraq, adding that the administration has "got to be honest with our evaluation there."

Those kinds of comments have emboldened Kerry advisers, who believe it is time to make the Iraq debate one that looks forward. "Iraq is the defining issue of the Bush administration, and their attempt to make Kerry answer questions obscures the fact that it's they who should answer questions," said Kerry adviser Richard C. Holbrooke.

Holbrooke said Bush has gotten a free ride on Iraq for months and called the national intelligence estimate "a smoking gun" that could refocus the debate. "It shows two things," he said. "One is that the situation in Iraq is as bad as the more pessimistic observers have said. Two, that the president was aware of these assessments back in June and has been misleading the public ever since by concealing his own intelligence estimates."

Sen. Joseph R. Biden Jr. (D-Del.) said Kerry must "stop litigating what has been their [the Bush campaign's] deftness in taking advantage of a complicated issue," a reference to Kerry's struggle to explain his positions on Iraq.

"Start focusing on what's the plan, Stan," Biden said. "This administration wants to be judged on what they say is the central front of the war on terror which is Iraq. The president says we're doing well in Iraq. The president misunderstood, misjudged and misled the American people on Iraq consistently, since the fall of the statue of Saddam Hussein."

Kerry has run into two problems of his own making, aides say: He voted to authorize the war in 2002, says today the war is wrong but will not take back his vote; and he has yet to detail a markedly different strategy than Bush's for ending the conflict. This has allowed the president to argue -- with great success, Democrats say -- that Kerry and Bush basically agreed on the need to go to war and see eye to eye on how to get out.

Bush boxed Kerry into a situation where the Democratic nominee was "running in the same circles on the same questions," said Michael McCurry, the former White House spokesman under President Bill Clinton who was brought aboard this past week to sharpen Kerry's message. Moreover, polls show the president has convinced a large number of voters that Kerry is a flip-flopper whose word cannot be trusted.

McCurry admitted that this will be difficult to undo. Bush "paid a lot of money to drive up Kerry's negatives," he said. "Once you wear those negatives they put on you, it is hard to get them off."

The goal of Kerry's advisers is to change the dynamics of the debate. Kerry has reworked his stump speech with a new toughly worded indictment of the conditions in Iraq: the increasing number of deaths, the spread of terrorists and extremists, the growing clout of anti-American insurgents, and what some say are fading hopes for the country's first-ever democratic elections in January.

He also is punctuating the speeches by accusing Bush of misleading the nation about these problems. "He misled America step after step about what this is about and what is at stake," Kerry said Friday at town hall forum in Aurora, Colo. "We deserve a president who tells America the truth." It is not uncommon for Kerry to use some variation of "dishonesty" more than a dozen times in a 30-minute appearance now.

Amid daily reports of deaths in Iraq, Kerry is trying to portray Bush as disconnected from voters and reality when he offers optimistic assessments. "With all due respect to the president, has he turned on the evening news lately?" Kerry said Friday in Albuquerque. "Does he read the newspapers? Does he really know what's happening? Is he talking about the same war that the rest of us are talking about?"

Kerry advisers vow not to cede any ground to Bush as he performs his presidential duties this week at the United Nations and the White House with Allawi, but the president's advisers believe that, even amid concerns rising about Iraq, they can hold the high ground in the debate. "The reason the debate has served to strengthen the president's position and hurt Kerry's position is President Bush shows strength and resolve and Senator Kerry shows weakness and vacillation," Bush campaign manager Ken Mehlman said.

Bush used the Republican National Convention in New York to refocus public attention on the terrorist attacks of Sept. 11, 2001, as much as on the war in Iraq, hoping to solidify public confidence in his leadership in the war on terrorism. That day has an emotional hold on voters, and the Bush campaign effectively evoked the memories from the convention through the memorial services of last weekend.

"Now we're seeing something slightly different: all the problems in Iraq," Democratic pollster Peter Hart said. "No matter how we tote it, things are not going well in Iraq. I've always believed the number of days Iraq is on the front pages of the newspaper has direct impact on Bush's reelection."

.Democratic presidential candidate John F. Kerry recently began confronting President Bush on Iraq's progress toward democracy.