Iraq must do more to protect American and allied forces, an American official said after a civilian U.S. contractor was killed last week in an attack that left several other U.S. and Iraqi service members injured.

The U.S. blames the attack on an Iranian-backed militia group known as Kataib Hezbollah, an Iraqi militia group sponsored by Iran.

The official, who like a handful of others spoke to reporters on condition of anonymity, brushed off concerns that the Iraqi government could call into question its relationship with the U.S.-backed coalition after the U.S. launched a series of strikes on Sunday

Read more: US says Iraq must do more to protect its forces