BAGHDAD — American commandos are on the front lines in Syria in a new push toward the Islamic State’s de facto capital in Raqqa, but in Iraq it is an entirely different story: Iran, not the United States, has become the face of an operation to retake Fallujah from the militant group.
On the outskirts of Fallujah, tens of thousands of Iraqi soldiers, police officers and Shi’ite militiamen backed by Iran are preparing for an assault on the Sunni city, raising fears of a sectarian bloodbath.
Iran has placed advisers, including its top spymaster, Qassim Suleimani, on the ground to assist in the operation.
The battle over Fallujah has evolved into yet another example of how United States and Iranian interests seemingly converge and clash at the same time in Iraq. Both want to defeat the Islamic State.
But the United States has long believed that Iran’s role, which relies on militias accused of sectarian abuses, can make matters worse by angering Sunnis and making them more sympathetic to the militants.
While the battle against the Islamic State straddles the borders of Iraq and Syria, the United States has approached it as two separate fights.
In Syria, where the government of Bashar Assad is an enemy, America’s ally is the Kurds. But in Iraq, where the United States backs the central government, and trains and advises the Iraqi army, it has been limited by the role of Iran, the most powerful foreign power inside the country.
That US dilemma is on full display in Fallujah as the fighting intensifies.
Inside the city, tens of thousands of Sunni civilians are trapped, starving and lacking medicine, according to activists and interviews with residents. Some were shot to death by the Islamic State as they tried to flee, and others died under buildings that collapsed under heavy military and militia artillery bombardment in recent days, according to the United Nations.
The few civilians who have made it to safety have escaped at night, traveling through the irrigation pipes.
In an extraordinary statement Wednesday, Grand Ayatollah Ali al-Sistani, the world’s preeminent Shi’ite religious leader, who lives in Najaf in southern Iraq and is said to be concerned by Iran’s growing role in Iraq, urged security forces and militia to restrain themselves and abide by “the standard behaviors of jihad.’’
The grim tableau in Fallujah — starving Sunni civilians trapped in a city surrounded by a mostly Shi’ite force — provides the backdrop to a final assault that Iraqi officials have promised will come soon.
The United States has thousands of military personnel in Iraq and has trained Iraqi security forces for nearly two years, yet is largely on the sidelines in the battle to retake Fallujah.
It says its air and artillery strikes have killed dozens of Islamic State fighters, including the group’s Fallujah commander. But it worries that an assault on the city could backfire — inflaming the same sectarian sentiments that have allowed the Islamic State to flourish there.
Already, as the army and militiamen battled this past week in outlying areas, taking some villages and the center of the city of Karma, to the northeast, the fight has taken on sectarian overtones.
Militiamen have plastered artillery shells with the name of Sheikh Nimr al-Nimr, a Shi’ite cleric close to Iran whose execution this year by Saudi Arabia, a Sunni power, deepened the region’s sectarian divide, before firing them at Fallujah.
A Shi’ite militia leader, in a widely circulated video, is seen rallying his men with a message of revenge against the people of Fallujah, whom many Iraqi Shi’ites believe to be Islamic State sympathizers rather than innocent civilians.
Fallujah is also believed to be a staging ground for suicide bombers targeting the capital, Baghdad, about 40 miles east.
