The United States has called on Baghdad to "take actions" to protect US interests in the country after a flurry of attacks that have been blamed on Iranian-backed groups.
Tehran wields growing influence in Iraq, particularly through armed factions.
Since October 28, ten rocket attacks have targeted areas where US soldiers and diplomats are stationed.
They have not been claimed, but the United States has blamed Iranian-backed Shiite paramilitary groups.
US Defense Secretary Mark Esper told reporters Monday he had expressed "concern about the optics in attacks on bases in Iraq where US troops and material might be," in a call with outgoing prime minister Adel Abdel Mahdi.
The US has "a right of self defense, that we would ask our Iraqi partners to take proactive actions... to get that under control, because it's not good for anybody," he told Abdel Mahdi.
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Abdel Mahdi's office released a statement earlier Monday confirming the phone call and asking everyone "to spare no effort to prevent an escalation that will threaten all parties".
"Unilateral decisions will trigger negative reactions that will make it more difficult to control the situation and will threaten Iraq's security, sovereignty and independence," he said.
Esper, speaking on a plane returning from Belgium, where he had attended the 75th anniversary of the Battle of the Bulge, acknowledged Tehran's involvement was difficult to prove.
"My suspicion would be that Iran is behind these attacks, much like they are behind a lot of malign behaviour throughout the region," he said. "But it's hard to pin down."