PUSAN, South Korea, Friday, Nov. 18 - President Bush may have come to Asia determined to show leaders here that his agenda is far broader than Iraq and terrorism, but at every stop, and every day, Mr. Bush and his aides have been fighting a rearguard action to justify how the United States got into Iraq and how to get out.

On Friday morning, as Mr. Bush was meeting the leaders of Southeast Asia, his press secretary issued an unusually blistering statement responding to Representative John P. Murtha's call for a pullout from Iraq, declaring that Mr. Murtha, a Pennsylvania Democrat who had often backed Mr. Bush's military initiatives, was "endorsing the policy positions of Michael Moore and the extreme liberal wing of the Democratic Party."

Standing Thursday with President Roh Moo Hyun of South Korea, Mr. Bush leapt on a question about the charges that he had manipulated prewar intelligence. "I expect there to be criticism, but when Democrats say that I deliberately misled the Congress and the people, that's irresponsible," he said, as Mr. Roh looked on silently.

On Friday morning, Mr. Roh's defense minister, Yoon Kwang Ung, announced that South Korea planned to withdraw about a third of its 3,200 troops from northern Iraq next year. While the step has been rumored for two months, it was unclear why it was announced while Mr. Bush was here.

But if Mr. Bush's aides were surprised about the timing, his hosts, both here and in Japan, have appeared surprised at Mr. Bush's tone, which has given them an unobstructed window into the growing debate in Washington about how the United States got into Iraq, and when it should get out.

"I think it has been a bit of a shock to everyone," said one longtime Japanese diplomat when Mr. Bush was in Kyoto, insisting on anonymity because he was not speaking for the government. He noted that Mr. Bush had publicly thanked Prime Minister Junichiro Koizumi for sending Japanese troops to Iraq in the face of overwhelming opposition in Japan. But the diplomat wondered whether "after the president leaves, there will be more and more questions about why we are there, too."

What Mr. Bush's Asian hosts have seen, however, is more than a vigorous defense of Iraq policy. For the first time, Mr. Bush and his aides have taken their critics by name, declared their motives to be entirely political, and suggested their approach would give aid and comfort to the terrorists.

The statement by the White House spokesman, Scott McClellan, Friday morning in response to Mr. Murtha, for example, declared that "the eve of an historic democratic election in Iraq is not the time to surrender to the terrorists."

The statement continued, "Nowhere does he explain how retreating from Iraq makes America safer."

It did not address, however, the core of Mr. Murtha's argument: that the American troops have become a "catalyst for violence" and that they should be replaced with a "quick reaction force" in the Middle East to keep stability without entering the middle of the fray.

Three times so far since Mr. Bush left Washington on Monday, the White House has also issued detailed rebuttals on Iraq issues under the rubric "Setting the Record Straight." One was devoted to answering an editorial in The New York Times on prewar intelligence, and two others responded to Democratic critics, quoting their own words about Iraq back to them, arguing that they, too, had believed Saddam Hussein possessed illicit weapons.

Talking to reporters on Thursday, Dan Bartlett, the counselor to the president who has played a central role in drafting many of the Iraq messages, said that Mr. Bush's decision to fight back - chiefly on the question of how he had used prewar intelligence - arose after he became concerned the debate was now at a tipping point.

"In the last couple of weeks it has reached a critical mass, and we felt we had to respond," Mr. Bartlett said in this port city, which, 55 years ago, was a battlefront of another American war, one that took three years to come to a slogging armistice.

"I think it's not only fair game for the president to correct the record, I think it's his obligation," he said.

Mr. Bartlett insisted the president was not trying to quash debate about Iraq. Rather, he said, the president was "blowing the whistle" on those who are "willfully and knowingly saying something that happens not to be true." But others around Mr. Bush are clearly concerned. One senior official said that inside the White House, there is now an active debate about whether Mr. Bush and his aides erred in not explicitly admitting to mistakes in how they conducted the war, the occupation, and the repeated efforts to train Iraqi troops.

"It's one of those things that get you either way," said the official, who insisted on anonymity because he was discussing internal White House debates. "If you open up a debate about what went right and what went wrong, there's no end of it. But if you take the position that we took - that we're looking to the future - you have to demonstrate progress."