US Secretary of State Mike Pompeo on Friday warned Iran of a "decisive" response if US interests are harmed in Iraq.
Mr Pompeo’s warning followed a series of rocket attacks targeting bases housing US forces in the country.
"We must... use this opportunity to remind Iran's leaders that any attacks by them, or their proxies of any identity, that harm Americans, our allies or our interests will be answered with a decisive US response," Mr Pompeo said in a statement.
"Iran must respect the sovereignty of its neighbours and immediately cease its provision of lethal aid and support to third parties in Iraq and throughout the region," he said.
The United States has expressed mounting concern about the flurry of attacks on Iraqi bases used by US troops, several of which it has blamed on Iranian-backed Shiite paramilitary groups.
Two rockets were fired at a base housing US troops near Baghdad airport on Thursday, the tenth such attack since late October, the Iraqi army said.
The attack followed one targeting the same base on Monday which wounded six members of Iraq's elite US-trained counter terrorism force, two of them critically, the army said.
Mr Pompeo, who has repeatedly warned Tehran, pinned the blame for the latest attacks squarely on "Iran's proxies".
Iran has exerted significant influence in Iraq since the 2003 US invasion brought down Saddam Hussein.
President Donald Trump's administration has been trying to counter Tehran's influence around the region, including through sanctions aimed at blocking all its oil exports.
