Washington  - Democrat Barack Obama waded into the heart of Republican country on US Independence Day Friday after provoking a storm of debate over his intentions for Iraq if elected president in November.

He chose Butte, Montana, to deliver his Fourth of July speech, the most recent stop of his week-long swing through conservative territory with messages on patriotism in Missouri, faith-based social services in Ohio and public service in Colorado.

The moves, seen as a strategy to court the political centre after the primary elections, have provoked outcry among his liberal base.

Over the past weeks, he also alienated some hardcore followers over his apparent support of the death penalty for convicted rapists and agreement with a Supreme Court ruling that supported handguns.

On Thursday, he delivered another surprise with seemingly contradictory comments on Iraq, raising the possibility that if elected president, he may slow down his pledged
16-month withdrawal from Iraq if military commanders believed US troops would be put at risk.

Early in the day, he said he planned a "thorough assessment" and refinement of his Iraq policy after he visited Iraq and spoke to commanders.

"My 16-month timeline, if you examine everything I've said, was always premised on making sure our troops were safe," Obama was quoted as telling reporters on his campaign plane as it landed in North Dakota.

Later in the day, after a media storm over his remarks, he came back to the issue before leaving North Dakota to clear up any misunderstanding, vowing "to end this war."

Centre-right Republican John McCain, his party's presumptive nominee, wasted no time to jump in.

McCain's campaign charged political expediency, insisting that Obama's comments showed his "past positions to be just empty words" and welcoming Obama to McCain's position "that we cannot risk the progress we have made in Iraq by beginning to withdraw our troops immediately without concern for conditions on the ground."

Obama's campaign fired back an e-mail to the media, using quotes dating back to 2007 to prove that his remarks on Thursday were in keeping with his past stance. Obama has repeatedly charged that McCain is committed to an indefinite presence in Iraq.

McCain, picking up on the increasing anti-war mood in the country, himself has moved away from his primary campaign pledge to keep troops in Iraq for 100 years if necessary, saying he would remove most troops by 2013.

The moves by both candidates represent the typical movement-to- center after the primary election campaigns, when they pitch extreme conservative or liberal messages to committed supporters to secure their party's support.

One Maryland Democrat who staunchly supported Hillary Clinton against Obama greeted his cultivation of the vast conservative US voter base.

"I'm pleased that he's reasessing his position," she said, on condition of anonymity. "It's a tough world out there. This is not a game for wimps. He's demonstrating that he can be hard-nosed." (dpa)