"I was a little puzzled by the frenzy that I set off by what I thought was a pretty innocuous statement," the presumptive Democratic presidential nominee told reporters flying with him to Missouri from Montana. "I am absolutely committed to ending the war."

On Thursday in North Dakota, Obama said that "I'll . . . continue to refine my policy" on Iraq after a forthcoming trip there. With a promise to end the war the central premise of his candidacy, the Obama campaign has struggled over the last two days to push back against Republicans and others who say his recent statement could be a softening.

In two news conferences on Thursday, Obama said any refinement of his position on Iraq wouldn't be related to his promise to remove combat forces within 16 months of taking office, but rather to the number of troops needed to train Iraqis and fight al-Qaeda. But he also acknowledged that the 16-month time line could indeed slip if removing troops risked their safety or Iraqi stability.

"What's important is to understand the difference between strategy and tactics," he told reporters. "The tactics of how we ensure our troops are safe as we pull out, how we execute the withdrawal, those are things that are all based on facts and conditions. I am not somebody - unlike George Bush - who is willing to ignore facts on the basis of my preconceived notions."

Noting that "we want to build on" the lessening of violence in Iraq, he added: "It doesn't change my strategic view that we have to bring our occupation to a close."

He said he didn't misspeak in his comments earlier in the week and suggested the media and critics read unintended significance into the remarks.

"I was surprised by how finely calibrated every single word was measured," Obama said. "I wasn't saying anything that I hadn't said before."