Commanders in Iraq have decided to begin the draw down of US forces in volatile Diyala province, marking a turning point in the US military mission.

Instead of replacing the third Brigade of the first Cavalry Division soldiers from another brigade in Salahuddin province will expand into Diyala.

In this way, the number of US Army ground combat brigades in Iraq will fall from 20 to 19.

It will also mark the start of what President George W Bush has billed as a shift in the American military mission.

The December move, not yet announced by the Pentagon, was described by Col Stephen Twitty, commander of the fourth Brigade, first Cavalry, in a telephonic interview.

Three other officials confirmed it in Iraq, including Lt Col Michael Donnelly, chief spokesperson for the commanding general of US forces in northern Iraq, Major Gen Benjamin Mixon.

The idea is to avoid vacating a contested area, like Diyala, while beginning Bush's announced reduction of at least 21,500 troops, of which 17,000 were sent to the Baghdad area last spring.

The shift in Diyala in December could be a model for follow-on reductions next year, with a redrawing of the US lines of responsibility so that a departing brigade has its battle space consumed by a remaining brigade.

At the same time, Iraqi security forces would assume greater responsibility.

Former Vice President Al Gore said that he has no plan to join the U.S. presidential race even after winning the Nobel Peace Prize for urging global action to fight climate change.

Gore, narrowly beaten by President George W. Bush in the 2000 race, said that it was a "great honor" to win the prestigious award, announced in Oslo on Friday. Gore will share the $1.5 million prize with the U.N. climate panel.

"I don't have plans to be a candidate again so I don't really see it in that context at all," Gore said when asked in an interview with Norway's NRK public television aired on Wednesday about how the award would affect his political future.

NRK said it was Gore's first interview since the prize revived speculation that he might make a late bid for the Democratic nomination for the 2008 presidential election.

An organization called www.draftgore.com said that 200,000 people had signed a petition to urge Gore to run, with a jump of 70,000 signatures in four days after the prize.

"I'm involved in a different kind of campaign, it's a global campaign," Gore said. "It's a campaign to change the way people think about the climate crisis."

Gore has repeatedly said that he has no plans to run, without completely ruling it out, in a crowded Democratic field against Hillary Clinton, Barack Obama and John Edwards.

It would be hard, but not impossible, for Gore to enter the race. The first contest on the road to the election in November 2008, the Iowa caucuses, are less than 100 days away.