As negotiations on a possible nuclear deal approach a March 31 deadline, U.S. officials are increasingly alarmed about Iran’s expanding military presence in Iraq — and the threat it may pose to American soldiers in the country.

Two scenarios are of particular concern, officials say. One is that a collapse of the nuclear talks could escalate tensions between Iran and the U.S., emboldening Iranian hard-liners and potentially leading to attacks on Americans in Iraq.


The other is that increased U.S. efforts to oust Syrian president Bashar Assad, a close ally of Tehran, could provoke retaliation from Iran. White House officials who oppose greater involvement in Syria’s civil war often cite concern for the safety of Americans in Iraq as a reason for caution, sources said.

In either case, U.S. officials fear, Iran could direct the Iraqi Shiite militias under its control to attack U.S. troops aiding the fight against the Islamic State in Iraq and the Levant.

“The current [nuclear] negotiations likely have a restraining effect, but there are other incentives and national interests at stake for the Iranians,” said a senior U.S. military official. “This is something that we are continually assessing. [Iran’s] history as regional provocateurs and exporters on terrorism demands it.”

President Barack Obama has dispatched 3,000 troops to Iraq as trainers and advisers to Iraqi forces battling ISIL. Many are now in close proximity to heavily armed Shiite militias with direct ties to Tehran. At times, the militias have even fought in tacit cooperation with the U.S.

But while Iran may be the enemy of America’s enemy, U.S. military officials don’t consider it a friend. They bitterly recall Iran’s role during the Iraq war, when roadside bombs sent by Tehran to Shiite militias who fought the U.S. occupation killed hundreds of American troops. Some of those same militias have now remobilized to battle the Islamic State of Iraq and the Levant, a Sunni Muslim group that considers Shiites apostates and that has seized vast swaths of territory in northern Syria and western Iraq.

In particular, the U.S. holds responsible Maj. Gen. Qassem Suleimani, who commands Iran’s secretive Quds Force. Suleimani and other Iranian commanders are now in Iraq directing Shiite fighters against ISIL

“We declare to the world, we have Iranian advisers, and we’re proud of them, and we thank them deeply for participating with us,” Hadi Al-Amari, leader of the Shiite paramilitary force Hashd Al-Shaabi, told CNN earlier this month.

The allegiances of many Iraqi Shiite fighters are no secret. Some openly display posters of Iran’s Supreme Leader, Ali Khamenei, who recently commended a Tehran crowd for chanting “Death to America.”

The concern is that those fighters, under the direction of Suleimani, may again train their sights on American troops.

“The U.S. military is very concerned that the Iranians will come after American personnel in Iraq,” says Kenneth Pollack, a former CIA analyst and Brookings Institution scholar close to the Pentagon. “It’s clearly something that’s been on their mind for a while.”

One military official said there is no imminent Iranian threat to Americans in Iraq, who operate from the U.S. Embassy in Baghdad and from joint command centers with Iraqi and Kurdish forces.

But sources said the potential danger is factored into U.S. military planning. Debates about troop levels in Iraq, for instance, are shaped in part by concerns that a larger force creates a bigger potential target for Iran.

While not in front-line combat roles, the Americans could be vulnerable to attacks on their compounds. Ducking and covering from rocket and mortar fire was a routine part of life for Americans stationed in Iraq during the U.S. occupation there.

“That’s a fresh memory for people,” said Derek Chollet, who left a top Pentagon post in January and is now with the German Marshall Fund.

Iran’s ability to harm American troops in Iraq has also shaped another major Obama administration debate, sources said: whether to step up efforts to depose Syria’s Assad.

The Obama administration says its priority is to defeat ISIL — despite pressure from Arab allies who want to go after Assad more directly — and calls that the sole mission of the Sunni rebels it is training and equipping under a nascent Pentagon program based in Saudi Arabia.

“Multiple [officials] have told me they’re worried about retaliation in Iraq, which does seem to be influencing our Syria policy,” says Robert Ford, who served as Obama’s liaison to the Syrian rebels until last summer. “Basically, they’re afraid that if they provide serious help to the armed opposition against Assad, the Iranians will have their surrogates in Iraq attack us.”

Iran has spent billions of dollars to help the Syrian dictator, a longtime conduit for Iranian influence in the region, survive that country’s sectarian civil war.

Obama officials believe that Iran has avoided threatening American troops in Iraq because they welcome the U.S. air campaign against ISIL, which has massacred Shiites and attacked their shrines.

Iran has also avoided actions that could derail the nuclear talks, which are headed for a key deadline at the end of this month when negotiators from the U.S. and five other nations hope to reach a framework agreement with Iran limiting its nuclear program in return for sanctions relief.

But many Republicans in Congress want to derail what they fear will be a bad deal with Iran. Obama has warned that the collapse of the nuclear talks would increase the chance of possible U.S. military action against Iran. Such talk in Washington would increase the risk to the Americans based in Iraq.

Even if a nuclear deal is struck, Iran can tolerate an American presence in neighboring Iraq for only so long, according to Ford, who served as political counselor to the U.S. Embassy in Baghdad from 2004 to 2006.

“They don’t want American troops in Iraq,” Ford said. “They’re going along with it now because they need us. But as soon as the Islamic State is contained or degraded sufficiently they will want us to leave — and they will encourage us by a variety of means, including mortar strikes and rocket strikes.”

Ominously perhaps, Amari, the Shiite militia leader, told CNN that Iraq doesn’t need America’s help in defeating ISIL.

Persistent fears that Iran may try to target Americans in Iraq underscore the difficulty of thawing relations between Washington and Tehran. So do other Iranian activities opposed by the U.S., including Iran’s support for Hezbollah in Lebanon and for the Houthi rebels who recently ousted Yemen’s government.

“It does point up the fact that we have a huge problem with Iran outside of the nuclear space,” said Chollet. “And that will continue to exist even if we get a nuclear deal.”