The US Department of Defense officially confirmed two attacks by pro-Iranian militias on US forces in Iraq and Syria on Sunday.
"On April 22, Iran aligned militia groups conducted two unsuccessful attacks on US forces in Iraq and Syria," Pentagon spokesman Pat Ryder said in Washington on Tuesday.
"These attacks put coalition and Iraqi personnel at risk and call on the Government of Iraq to take all necessary steps to ensure the safety of US forces in Iraq and Syria against attacks from these groups," Ryder said.
No US military personnel were injured.
On Monday, the US Department of State had mentioned an attack by an Iran-aligned militia group on a US military base in Syria. The Department of Defense said that a coalition fighter had destroyed a launcher in self-defence after reports of a failed rocket attack near the coalition base at Rumalyn in Syria.
Since the war in the Gaza Strip broke out in October, pro-Iranian militias have repeatedly attacked bases in Iraq and Syria also used by the US military.
At the end of January, three US soldiers were killed in one of the attacks in Jordan near the Syrian border.