Disengaging from Afghanistan is the option President Barack Obama is the least likely to adopt as he closes in on a new strategy in the eight-year war he calls one of “necessity.”

But on Thursday, at one of the countless policy conferences in Washington to discuss the president's choices, some experts suggested withdrawal was the best route — and they said it would not necessarily impact efforts to fight al Qaeda.

Harvard University's Stephen Walt called the argument for disengagement “fairly compelling,” while conceding it was not the most popular.

His tally of the costs: $225 billion since the Sept. 11 attacks, with more than 850 U.S. soldiers killed and thousands wounded.

“The costs are going to be large at a time when the American economy is not exactly robust,” he told the Capitol Hill conference organized by the Rand Corporation.

Even if  the United States “won,” al Qaeda would still have a safe haven in neighboring Pakistan as well as in Yemen, Somalia or other nations where they like to hang out, Walt said. If U.S. forces withdrew from Afghanistan, “it is not obvious that it  will significantly enhance al Qaeda's ability to go after us.”

The CATO Institute's Christopher Preble was also in the “big skeptic” column when it comes to sending in more U.S. troops to Afghanistan. He said the big question Obama needs to ask is whether the mission in Afghanistan is essential for U.S. national security — which most experts argue it is.

“Has it become a case of we must win the war because it is the war that we are in?” asked Preble. “We must narrow our focus. We don't need a large-scale, long-term presence to degrade al Qaeda's capacity in Afghanistan.” 

Countering Preble and Walt, was Afghanistan expert Jim Dobbins who argued that the consequences of pulling out would be an escalation of the civil war, a region further destabilized and even more misery for the Afghan population. “You will see hardship that makes what you see now look like prosperity,” said Dobbins, with the Rand Corporation.

Also pounding on the withdrawal drum was the anti-war group Code Pink, whose representative pressed Senator Carl Levin to follow public opinion and push for a pull-out.

But Levin, who is calling for more U.S. and NATO trainers to go to Afghanistan to double that country's police and army forces, said Obama was doing his best to advance the country's national security interests.

“When President Bush decided to go to Iraq, public opinion supported him. I don't' think you did. I didn't either,” answered Levin to Code Pink's Medea Benjamin.

On Friday, the commander-in-chief  meets his military chiefs to hear recommendations on troop strength. Officials say his deliberations are coming to a close in what will be known in decades to come as Obama's war.

Which side of the fence are you on?