Barack Obama battled charges that he was reinventing his plan for withdrawal from Iraq Thursday, carving out a nuanced military policy after saying earlier in the day that he might "refine" his Iraq approach.

The earlier statement was widely interpreted as a willingness to revise his long-stated plan to withdraw all brigades within 16 months of taking office, and opened him up to Republican attacks.

But the backlash led Obama to call a second press conference in Fargo, N.D., where the presumptive Democratic presidential nominee said he was not talking about refining his 16-month timetable.

"I have not equivocated on that position, I am not searching for maneuvering room with respect to that position ," he said. “I’m just puzzled …I think what’s happened is that the (John) McCain campaign primed the pump with the press to suggest that somehow we were changing our policy when we haven’t, and that just hasn’t been the case.”

GOP criticism Thursday initially came from the Republican National Committee, which in a statement said: "There appears to be no issue that Barack Obama is not willing to reverse himself on for the sake of political expedience."

But his second press conference touched off a new round of recriminations.

The RNC repeated its charge, and McCain spokesman Brian Rogers said Obama has "reversed" his position.

"Now that Barack Obama has changed course and proven his past positions to be just empty words, we would like to congratulate him for accepting John McCain's principled stand on this critical national security issue. If he had visited Iraq sooner or actually had a one-on-one meeting with General Petraeus, he would have changed his position long ago," Rogers said in a statement.

Obama seemed to struggle Thursday in explaining how his upcoming trip to Iraq might refine, but not basically alter, his promise to quickly remove U.S. combat troops from the war.

In Obama's first press conference of the day, the long-time opponent of the Iraq war said his coming trip to the Middle East would be a chance to assess his military goals, and suggested he would not jeopardize Iraq security in pursuit of a timetable.

"I have always said that I will listen to commanders on the ground. I've always said that the pace of withdrawal would be dictated by the safety and security of our troops and the need to maintain stability," Obama told reporters.

"That assessment has not changed, and when I go to Iraq and I have a chance to talk to some of the commanders on the ground, I'm sure I'll have more information and will continue to refine my policies."

During the Democratic primary, Obama said repeatedly that he would end the Iraq war in 2009.

Obama's Web site says he would immediately begin removing troops from Iraq upon taking office. It says he would remove one to two combat brigades each month, and have all brigades out of Iraq in 16 months.

Obama said Thursday afternoon that's still the plan. He said that the only refining he was talking about had to do with training for Iraqi military and police, and troop presence for counter-terrorism strike teams.

He promised to summon the Joint Chiefs of Staff on his first day in office "and I will give them a new mission and that is to end this war, responsibly and deliberately, but decisively."

The campaign sent around a list of past Obama statements to show that he has been consistent in saying he would listen to commanders on the ground and that he is open to tactical adjustment.

But it was unclear how much wiggle room he was giving himself with the 16-month timetable.

Earlier in the day he said: "My 16-month timeline ... was always premised on making sure that our troops were safe ... And I'm going to continue to gather information to find out whether those conditions still hold."

And at his second press conference, he said: “If it turned out, for example, that we had to, in certain months, slow the pace (of withdrawal) because of the safety of American troops … of course we would take that into account."

There have also been mixed messages coming out of Obama's supporters.

Missouri Sen. Claire McCaskill, a campaign co-chair, told MSNBC Tuesday, "No. No, he will not (change his Iraq policy) ... Now is the time that we need to carefully and reasonably withdraw."

Obama foreign policy adviser Susan Rice told the same network on the same day that the 16-month plan was a "timetable," not a deadline, and that Obama would listen to commanders to devise his Iraq strategy.

Republicans seized on McCaskill's statement. Virginia Rep. Eric Cantor said on a McCain conference call Wednesday that McCaskill "demonstrated his unwillingness to change direction."

"I guess the question is, if ... he's going to go to Iraq and nothing that he sees will change or impact his decision-making on this, then why is he going?" Rogers said. "And if it's just to check a box, politically, then it, sort of, represents ... the kind of cynical politics that most people ... are pretty sick and tired of."

Obama has scheduled a trip to Europe and the Middle East that includes stops in Jordan, Israel, the United Kingdom, Germany and France. Obama's campaign announced recently that he also plans to head to Iraq and Afghanistan over the summer as part of a congressional delegation, answering complaints from McCain and other Republicans that he has not visited the region since January 2006.

"I'm going to do a thorough assessment when I'm there," Obama said.

FOX News' Bonney Kapp and Major Garrett and The Associated Press contributed to this report.