Nearly four months after the fall of Ramadi, the American-backed effort by the Iraqi army to retake the provincial capital from Islamic State militants is moving slowly and fueling concerns that the Iraqis are not up to the task.

"I don't think there is any stomach to retake Ramadi right now and suffer the kind of causalities that such a battle would incur," said retired Army Col. Peter Mansoor, who served in Iraq in 2007 and 2008 as executive officer to retired Army Gen. David Petraeus, who led the war effort at that time. Mansoor now teaches military history at Ohio State University.

Others say the Iraqi army suffers from a debilitating lack of manpower and has never restored its force structure after the mass desertions in 2014 following the Islamic State's initial advance into Iraq.

"They can clear, but they can't hold. They are just going through the same areas over and over," said Joel Wing, an Iraq expert who tracks daily Arabic language news reports on his blog, Musings on Iraq.

He pointed to the examples of Husaybah and East Husaybah, which lie several miles east of Ramadi. Those towns were repeatedly targeted for clearing operations this summer, Wing said.

The total Iraqi force in Anbar province is about 10,000 to 15,000 soldiers, a far smaller number than the estimated 30,000 troops the Iraqis rallied for the battle of Tikrit in March, he said.

The fall of Ramadi to Islamic militants May 17 was a blow to the Pentagon's claims that the militant group, also known as ISIS and ISIL, was on the defensive. It also marked an inflection point for the Obama administration's policy and led to the deployment of about 450 additional U.S. troops to Iraq, setting up a U.S. outpost at Taqaddum Air Base and boosting direct U.S. support to local Sunni tribal militias.

Initially, many Iraqi and U.S. officials vowed to retake the city in a matter of days. But ISIS quickly fortified the city's perimeter with trenches, improvised explosive devices and snipers.

While the Iraqis officially have begun an operation to retake Ramadi, it remains in the "isolation phase" and has made limited inroads into the dense city center, U.S. officials say.

"It is a very challenging fight and the Iraqis are moving on the timeline that they've set for themselves," Air Force Col. Pat Ryder, a spokesman for U.S. Central Command, said recently. "In terms of when we get to the 'seize phase,' I'm not going to speculate about that."

Among the Iraq military's major problems is the absence of a strong chain of command. Thousands of fighters in Anbar are not Iraqi army soldiers but rather members of Shiite militias, which operate independently and often do not coordinate with the traditional forces under the Iraq Ministry of Defense.

"Sometimes they just go off and do whatever they want to do," Wing said of the militias.

The Iraqi army's failure to aggressively attack Ramadi is raising questions about the pillar of U.S. policy that avoids directly arming the Sunni tribal forces and prefers to provide money and weaponry via the Shiite-led central government in Baghdad.

Sunnis complain that the Shiite leaders in Baghdad don't want to supply Sunni tribal forces for fear those Sunnis will join the anti-government extremists.

Mansoor said there are important parallels between the current crisis and the so-called Sunni Awakening in Iraq about a decade ago, when dozens of Sunni tribes severed their alliance with Islamic extremist groups and began fighting alongside U.S. troops, a development that significantly reduced violence nationwide.

One of the parallels is that the Awakening gained strength when U.S. leaders, especially Petraeus, decided to support it with U.S. resources, Mansoor said.

"Currently we can't do that because any support for Sunni tribal fighters has to be funneled through Baghdad, which is loath to pass any assistance on to Iraqi Sunnis," he said. "This is in part a question of political will in Baghdad, but also calls into question whether the U.S. should be arming Sunni tribes as well as Kurdish forces rather than just funneling assistance through a government that doesn't like them."

The long-term worry that Iraq's three main factions — Sunnis, Shiites and Kurds — may never coalesce into another functioning state is gaining some traction.

Army Gen. Ray Odierno, a former commanding general in the Iraq War, said recently that a future Iraq "might not look like it did in the past."

Asked specifically about partition, or dividing up the country into three parts, Odierno said: "I think that is for the region and politicians to figure out, diplomats to figure out how to work this, but that is something that could happen. ... It might be the only solution. But I'm not ready to say that yet."

Defense Secretary Ash Carter said the current U.S. strategy of relying on local allies on the ground to fight the Islamic State might take time, but will be more successful in the long run.

"We could defeat ISIL — the U.S. military could defeat ISIL. That's not the trick," Carter told a group of service members on Sept. 1. "The trick is to defeat ISIL in a lasting way, and that means that after they're defeated, they need to stay defeated, which means that there need to be local forces representing the local people who keep the kind of extremism that ISIL represents from taking over again.

"You can't defeat ISIL from the outside in, there has to be an inside-out aspect to it. Otherwise, it won't stick ... and we'll be back there in five years, back there in 10 years, back there in 15 years. So we're looking for a lasting defeat."