Barack Obama, seeking to appeal to centrist voters in stops in traditionally Republican territory, said his upcoming trip to Iraq would help him refine his policy on troop withdrawals.
The Democratic presidential hopeful, in a stop in Republican stronghold North Dakota, at first appeared to suggest that he would reconsider his plan to withdraw US troops from Iraq within 16 months if elected.
The comment drew immediate criticism from Republicans, with the national party spokesman accusing him of changing course yet again on a major policy issue.
Mr Obama quickly called a second news conference, accusing supporters of Republican rival John McCain, of distorting his remarks. But the comments, and the exchange, underscored the stakes in a presidential race in which swing voters - courted by both Mr Obama and Mr McCain - are expected to play in the November elections.
Mr McCain has been a vocal supporter of the Iraq war and has expressed opposition to pulling out US troops until the Iraqis are able to manage their own security - positions that have opened him up to criticism from the Illinois senator.
Mr Obama has argued that Mr McCain offers little more than a continuation of President George Bush's policies and the unpopular war.
Mr Obama, in the second news conference, said what he learns from military commanders on his upcoming trip will refine his policy, but "not the 16-month timetable" for withdrawing US troops from combat in Iraq.
He said what he learns could affect how many residual troops might be needed to train the Iraqi army and police.
"I have said throughout this campaign that this war was ill-conceived, that it was a strategic blunder and that it needs to come to an end," he said.
"I have also said I would be deliberate and careful about how we get out. That position has not changed. I am not searching for manoeuvring room with respect to that position."
The back-and-forth over Iraq came as Mr Obama pushed forward into Republican strongholds such as North Dakota, Missouri and Montana, which has voted Republican for the White House by a hefty margin for almost four decades.
Mr Obama also said "mental distress" should not qualify as a justification for late-term abortions, a key distinction not embraced by many supporters of the procedure.
In an interview this week with Relevant, a Christian magazine, Mr Obama said prohibitions on late-term abortions must contain "a strict, well defined exception for the health of the mother".
Mr Obama then added: "Now, I don't think that 'mental distress' qualifies as the health of the mother. I think it has to be a serious physical issue that arises in pregnancy, where there are real, significant problems to the mother carrying that child to term."
Mr McCain, meanwhile, wrapped up a three-day visit to Colombia and Mexico to promote free trade and burnish his foreign policy credentials.
On Thursday, Mr McCain made a highly symbolic stop at Mexico City's famed Basilica de Guadalupe, Mexico's holiest site for Roman Catholics, and received a blessing from its monsignor.Reuse content