Photos appearing to show the leader of Iran's powerful Quds Force, Qasem Soleimani, liaising with Iraqi authorities near Baghdad have prompted speculation — and concern — over the role Iran and its proxies intend to play in driving ISIS out of Mosul and Fallujah.

Soleimani's presence in Iraq amid two major counter-ISIS offensives — in Fallujah, 30 miles west of Baghdad, and in Mosul, further north — has unnerved those familiar with Iran's campaign to cultivate influence in the region through Shiite proxy militias, whose presence in Sunni-majority areas could provoke sectarian violence.

"I can't emphasize enough how alarmed I am over these photos of Soleimani," Ali Khedery, the longest continuously serving US official in Iraq, told Business Insider in an interview. "Iran has a formal campaign of cultivating Shiite proxies, and those proxies have now been put on the Iraqi government's payroll in the form of the PMU."

The PMU, or Popular Mobilization Units (Hashid Shaabi), is a state-sponsored umbrella organization of predominantly Shiite militias. Critics say that they have contributed to, rather than eased, the kind of sectarian tensions that made Mosul and Fallujah susceptible to an ISIS takeover in the first place.

A member of the Iraqi security forces fires artillery during clashes with ISIS militants near Fallujah, Iraq. Reuters/Alaa Al-Marjani

Iraqi officials deny that the PMU is supported by Iran, but Soleimani's presence in Iraq suggests that Tehran is likely playing a significant military role there — and that the US is letting it happen.

Michael Weiss, coauthor of the book "ISIS: Inside the Army of Terror," tweeted that Soleimani's "presence is clearly tolerated" in Iraq. "And he looks quite relaxed."

The PMU's deputy chair, Abu Mahdi al-Muhandis — a US-designated terrorist — also arrived in the western Baghdad neighborhood of Arimiyah on Tuesday to oversee operations in western Fallujah, according to the Institute for the Study of War.

"What worries me most is the fact that Washington hasn't learned the lessons of the pre-surge era in Iraq," Khedery added, referring to the 2007 increase in US troops deployed to Baghdad and Al-Anbar Province.

The surge coincided with a new counterinsurgency strategy implemented by Gen. David Petraeus. It aimed at building long-term relationships with the local Iraqi population and security forces instead of focusing on killing Sunni insurgents, which had created a cycle of alienation and mistrust.

Institute for the Study of War

"You cannot defeat a radical Sunni extremist group like ISIS with radical Shiite extremists," said Khedery, who served as a special assistant to five US ambassadors and as a senior adviser to three heads of US Central Command. "It will only push more Sunnis into ISIS's hands. You need another tribal awakening that will allow moderate Sunni Arabs to retake their own areas."

US officials seem to be aware of the problem — one official told The Daily Beast's Nancy Youssef earlier this month that "Sunnis see ISIS as their protection — their wall against Shia revenge." The New York Times reported last week that US officials are worried about the role Iran will play in recapturing Fallujah.

But because the PMUs have been one of the most effective forces fighting ISIS in Iraq, the Obama administration has not seriously challenged Iraqi Prime Minister Haider al-Abadi's decision to allow the units' Shiite militias to help drive ISIS out of its strongholds. Iraqi and Western officials have insisted that the PMUs have taken only a secondary role in anti-ISIS operations.

Shiite fighters and Iraqi security forces advance toward Fallujah, Iraq, on May 25. Reuters

Khedery, for his part, predicted that Washington's tolerance for the militias will ultimately be the fatal flaw in its plans to defeat the Sunni extremists.

"What bothers me enormously is how shortsighted US policy continues to be with regard to Iraq," Khedery said. "The Obama administration is willing to provide Soleimani [and his proxies] with virtually unending support for the sake of the anti-ISIS campaign."

"We will thus win the battle, but we will certainly lose the war," Khedery added. "The US is unwittingly priming the Middle East for endless sectarian war, and that will certainly haunt the world for decades to come."

A 'prototype' for Mosul

Still, many experts agree that, currently, the main forces attacking ISIS in Fallujah are not the PMUs but Iraq's multiethnic counterterrorism units, which are being assisted by local tribal communities.

The offensive is a "prototype" for the kind of cooperation between local and government forces against ISIS that helped drive ISIS out of Ramadi last year, according to Ahmed Rushdi, a political analyst and director of the House of Iraqi Expertise Foundation.

"What is happening now in Falluja is paving the way for what will happen in Mosul on a much larger scale," Rushdi told Al Jazeera on Monday.

The Iraqis had slowly been recapturing territory from ISIS around Mosul, which fell to the jihadists in 2014, before the government announced a new offensive on Fallujah last week.

Saad al-Muttalibi, an adviser to the Iraqi Council of Ministers, agreed.

"All of the PMUs have been ordered not to enter Falluja," he told Al Jazeera. "Only the Iraqi Special Forces have entered the city. The PMUs are controlling the outskirts of Falluja."

Members of the Hashid Shaabi Shiite militia gather in the west of Samarra, in the desert of Anbar, as they prepare to depart for Mosul to fight against ISIS. Thomson Reuters

Still, Shiite forces within the PMU have been accused of attacking civilians in territory they have recaptured from ISIS. Reports have emerged that 17 civilians were killed by PMU fighters in the Garma district on the outskirts of Fallujah last week. Many Shiite forces believe that civilians in ISIS-held territory are sympathetic to the jihadists, even though Iraqi security forces helped nearly 800 civilians flee Fallujah late last week.

President Barack Obama has said repeatedly that he intends to "tighten the noose" around ISIS by training and supporting the Iraqi army. But, ultimately, few believe that that will be enough to halt ISIS's momentum in the country, which continues to be driven in large part by Baghdad's political instability, financial struggles, and the perception that Abadi — a member of Iraq's Shiite majority — is beholden to Iran.

"Abadi was and is a weak compromise candidate heavily influenced by Iran and its proxies," Michael Pregent, a former embedded adviser with a Peshmerga battalion operating in Mosul and former US Defense Department adviser, told Business Insider earlier this month.

"The US has no leverage in Baghdad," Pregent added, "which has long since been ceded to Tehran."