Robert Gates, named to replace Donald Rumsfeld at the Pentagon, is widely expected to change US policy in Iraq, but strategic and tactical options appear limited.
"What Rumsfeld's successor might do is not certain. The Baker-Hamilton Commission is reportedly very close to delivering recommendations. Gates himself is a long-time Bush family ally, having served under George HW Bush at the CIA," said Michael Moran, an expert at the Council on Foreign Relations.
In any event "as long as Rumsfeld was there, it was clear to the world and everyone there'd be no change in policy. So (his departure) was a necessary pre-condition but it's not a solution," said Senator Joseph Biden, a Delaware Democrat.
"I'm certain that Gates will come in with some of his own ideas, new ideas, new initiatives. I have confidence that he can help correct some" trouble areas, said Senator John Warner, a Virginia Republican.
With Rumsfeld's departure, ideas about "plan B" scenarios for Iraq are making the rounds in Washington from federalisation to gradual withdrawal of US troops, to a regional conference to sending in massive military reinforcements.
"Bad as the situation is today, it could get a lot worse if we simply pull out," said Max Boot, an expert at the Council on Foreign Relations.
"It would be a war of all against all. Iraq would probably degenerate into the kind of anarchy seen in Somalia and Afghanistan in the 1990s," he said in an editorial in The Los Angeles Times.
Lawmakers and experts are all eagerly awaiting conclusions of the independent Iraq Study Group led by former secretary of state James Baker, a Republican close to the Bush family as well as former Democratic lawmaker Lee Hamilton and Gates.
The group has looked at options including a gradual pullout of US troops and renewed dialogue with Iraq's neighbours, Iran and Syria.
"I hope that Baker and Hamilton will make a difference. I hope they'll make recommendations to start to re-deploy the troops. Because that's what this election was all about," Pennsylvania Representative John Murtha told CNN television.
Gates will "bring a specific change in the Defence Department. He'll listen to the military. He's got an open mind. He's experienced. The people will have confidence in him ... He won't reject the proposals of the military," Murtha added.
Biden recalled his federalisation plan for Iraq.
"My plan has been clear (...) And it is to get a political solution in Iraq, give the Sunnis a piece of the oil so they give up their insurgency, have a more federalised system as their constitution calls for, have a regional conference to keep the neighbours out and supporting whatever political solution that's reached inside," Biden said.
For Boot, "the only real hope of restoring order in the short term is to send American reinforcements. Unfortunately, pacifying the entire country would probably require 400,000 to 500,000 troops, an obvious non-starter.
A smaller number -- 25,000 to 50,000 -- might suffice to control Baghdad, but, in the current political climate, it seems unlikely that even that many will be sent. A few thousand extra troops won't make much difference."
Former US ambassador to the United Nations Richard Holbrooke has backed a regional conference to get support from Iraq's neighbours, and a redeployment of US troops to northern Iraq on the Turkish border.
Warner cautioned against radical change, saying, "You've got to remember the need to keep this government stabilised so that it can exercise sovereignty on behalf of the Iraqi people and to appear and actually convince the nations that border Iraq and in the region, that there's hope that Iraq can remain intact, not be subject to a civil war."
For US Senator Jack Reed, a Rhode Island Democrat, Gates "strikes me also as somebody who will listen, particularly to the uniformed services. And I think, in that respect, he will be a very pleasant change from secretary Rumsfeld."