The fall of Ramadi calls into question the Obama administration's strategy in Iraq.

Is there a Plan B?

The current U.S. approach is a blend of retraining and rebuilding the Iraqi army, prodding Baghdad to reconcile with the nation's Sunnis, and bombing Islamic State targets from the air without committing American ground combat troops.

But the rout revealed a weak Iraqi army, slow reconciliation and a bombing campaign that, while effective, is not decisive.

On Monday, administration officials acknowledged the fall of Ramadi, the capital of Anbar province, as a "setback" in America's latest effort in Iraq. They still maintained the campaign would ultimately bring victory.

But anything close to a victory appeared far off. The Islamic State group captured Ramadi over the weekend, killing up to 500 Iraqi civilians and soldiers and causing 8,000 people to flee their homes. On Monday the militants did a door-to-door search looking for policemen and pro-government tribesmen.

One alternative would be a containment strategy — trying to fence in the conflict rather than push the Islamic State group out of Iraq. That might include a combination of airstrikes and U.S. special operations raids to limit the group's reach. In fact, a Delta Force raid in Syria on Friday killed an IS leader known as Abu Sayyaf who U.S. officials said oversaw the group's oil and gas operations, a major source of funding.

Officials have said containment might become an option but is not under active discussion now.

It seems highly unlikely that President Barack Obama would take the more dramatic route of sending ground combat forces into Iraq to rescue the situation in Ramadi or elsewhere. A White House spokesman, Eric Shultz, said Monday the U.S. will continue its support through airstrikes, advisers and trainers; he pointed to an intensified series of coalition air assaults in the Ramadi area, which included eight strikes overnight Sunday.

The administration has said repeatedly that it does not believe Iraq can be stabilized for the long term unless Iraqis do the ground fighting.

Pentagon officials insisted Monday the current U.S. plan is still viable and that the loss of the city was merely part of the ebb and flow of war, not a sign that the Islamic State had exposed a fatal weakness in the Iraqi security forces and the U.S. strategy.

"We will retake Ramadi," said Col. Steve Warren, a Pentagon spokesman. The timing, he added, will be up to the Iraqi government.

Analysts are skeptical. Stephen Biddle, a George Washington University professor of political science who periodically advised U.S. commanders in Iraq during the 2003-2011 war, said Obama has been trying to split the Sunni tribes away from the Islamic State while pressing the Iraqi government to foster and rely on non-sectarian military forces.

"That's clearly not working, or at least it's not making the progress we had hoped it would make," Biddle said.

The Institute for the Study of War, which closely tracks developments in Iraq, said Ramadi was a key IS victory.

"This strategic gain constitutes a turning point in ISIS' ability to set the terms of battle in Anbar as well to project force in eastern Iraq," the institute said.

The full implication of Ramadi's fall is hard to define. But it almost certainly includes not only suffering for Ramadi's residents but also a delay in any Iraqi push to retake Mosul, the largest city in northern Iraq and an Islamic State stronghold since last June.

U.S. officials had said as recently as February that they hoped the Iraqis would be ready to march on Mosul by April or May, but those hopes had faded even before Ramadi was lost.

Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, issued a written statement Monday that suggested no change in approach.

"Setbacks are regrettable but not uncommon in warfare," Dempsey said.

Rep. Adam Schiff, the ranking Democrat on the House Intelligence Committee, said the U.S. should speed up the pace of arming Anbar's Sunni tribes and integrate them into the Shiite-dominated Iraqi military.

"The war in Anbar will not be won until the Sunni tribes feel they can protect themselves - from ISIS and the threat of militia abuses," Schiff said, referring to Iranian-backed Shiite militias.

Biddle sees corruption and sectarianism as "just too deep-seated to fix quickly."

That is one reason why Prime Minister Haider al-Abadi has turned to what his government calls popular mobilization units -- essentially Shiite militias. Al-Abadi says those units are under his government's control, although U.S. officials have expressed concern that their use in Sunni areas could create sectarian bloodshed that would push the country closer to all-out civil war.

By late Sunday, a large number of Shiite militiamen had arrived at a military base near Ramadi, apparently to participate in a possible counteroffensive, said the head of the Anbar provincial council, Sabah Karhout. Warren said Washington opposes outside military intervention if it detracts from the promotion of Iraqi sectarian unity.

Shiite militias played a key role in retaking the city of Tikrit from IS in April. After that success, al-Abadi set his sights on Anbar, saying its liberation was within reach. Instead, the Islamic State militants are now believed to control more than 60 percent of Anbar province, which stretches from the western edge of Baghdad all the way to Syria and Jordan.

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Associated Press writer Nedra Pickler contributed to this report.