(Updated: 8:53 a.m.) Democratic presidential hopeful Barack Obama says today he’ll propose “winding down” the U.S. troop presence in Iraq “in a way that is responsible” and improves the security of the United States.

Obama, a senator from Illinois, intends to unveil new policy proposals on troop withdrawals, diplomacy and dealing with Iraq’s humanitarian crisis in a speech at Ashford University in Clinton, Iowa,  the campaign said.

Among his proposals will be to call for a new constitutional convention in Iraq with the United Nations playing a central role.

He’ll also propose a renewed diplomatic effort, which his campaign said he wouldn’t hesitate to lead. The effort would include talking to Syria and Iran.

“I think there’s the potential there of a more constructive relationship when it comes to Iraq,” Obama said Tuesday in an interview with the Quad-City Times.

With Gen. David Patraeus, the top military commander in Iraq, and Ambassador Ryan Crocker testifying before Congress this week, the debate over the war has taken on an even more central role in the presidential campaign.

U.S. Sen. Chris Dodd, D-Conn., said Tuesday he is introducing a measure to tie war funding to withdrawing troops by April 30, 2008.

“I think in Iraq, it’s come to the point this is necessary,” Dodd said in a conference call.

John Edwards, meanwhile, has renewed his pressure on Congress not to pass a funding bill without a withdrawal timeline.

Obama would not discuss a date for when he might demand U.S. troops be withdrawn, and he would not say whether he would vote for a funding bill if it did not have a date for getting troops out. 

UPDATE: Obama's campaign announed early Wednesday that he will propose beginning a withdraw of combat brigades immediately, at a pace of on to two a month, to be completed by the end of next year.

He said that after his remarks today, “I want people to understand there is a way of winding down this commitment in a way that is responsible.”

With diplomatic and humanitarian efforts supplementing a withdrawal, he said, “we will not have a perfect situation in Iraq, but we will have a situation that actually improves the prospects of our long-term security.”

Aides said Obama will be more detailed about diplomatic efforts and how to deal with the humanitarian crisis, which would include a proposal to increase assistance to Iraqi refugees.

Ed Tibbetts can be contacted at (563) 383-2327 or etibbetts@qctimes.com.