"The situation needs resolution," said Larry DiRita, the Pentagon's chief spokesman and a close aide to Defense Secretary Donald Rumsfeld. "It can't remain indefinitely unresolved cause you've got a political transition that is taking place."

"People are making bets, they're taking a look and saying, 'Well, Jeez, if people can hold and attack the US military for weeks and weeks and weeks, then, shoot, I'm staying on the fence,'" he told reporters here.

Under an agreement worked out by marine commanders in Fallujah, marines began withdrawing Friday from positions inside the city while Major General Jassem Mohammed Saleh entered the city to lead an Iraqi security force that will replace the marines.

DiRita said marine commanders had "a lot of authority to make decisions, and they're doing that, and they've developed this force."

That may explain why senior Pentagon officials appeared to have been in the dark about the agreement on Thursday when it was first announced in Fallujah by marine officers.

General John Abizaid, the head of the US Central Command, told reporters earlier Friday he did not know the Iraqi general who was leading the force.

Pentagon officials likewise had little information about Saleh other than reports that he was a respected officer with a popular following.

DiRita indicated that Saleh's name was put forward by Iraqi ministry officials who have been involved in trying to find a negotiated solution to the crisis in Fallujah, where the killings of four US contractors a month ago ignited a battle for control of the city between insurgents and marines.

"Those people who share our objectives in a new Iraq have been helping identify who can be helpful in Fallujah," he said.

He said they included a group of former Iraqi generals.

"They are known to others we have been working with in the country, They have spent time with the US commanders," he said.

But DiRita admitted that it was a "far from perfect process."

"You scoop up people, you get them trained quickly and some of them turn out to be people you wish you hadn't. That's very possible here as well. It's something people are moving foward with with their eyes wide open," he said.

"The best vetting is public exposure," he said.

Abizaid, in a video teleconference with reporters from his headquarters in Qatar, expressed guarded optimism but also cautioned that it would take time to build confidence in the plan to turn over the city to the new Iraqi force.

"It's a step-by-step effort that will have to include a clear understanding of the security situation," he said.

"But the details of how we will build an Iraqi security capacity there will take some time. We need to have some patience," he said.

WAR.WIRE