Iraqi leaders have failed their obligations to keep American troops in the country safe from Iranian-controlled militias, according to U.S. officials.

“We have warned the Iraqi government many times, and we've shared information with them to try to work with them to carry out their responsibility to protect us, as their invited guests,” a senior State Department official told reporters Monday. “It's their responsibility and duty to protect us, and they have not taken the appropriate steps to do so.”

That rebuke was offered as a defense of U.S. airstrikes against Kataib Hezbollah, a militia that technically should report to Baghdad but is led by an Iraqi national with close ties to the Islamic Revolutionary Guards Corps. The airstrikes, which targeted three outposts in Iraq and two in Syria, have drawn complaints and threats from Iraqi political leaders and Iranian proxies.

“The prime minister described the American attack on the Iraqi armed forces as an unacceptable vicious assault that will have dangerous consequences,” Iraqi Prime Minister Adel Abdul Mahdi’s office said on Monday.

Iran raised the specter of retaliatory attacks against the United States. “Naturally, the brave people and heroic Hashd al-Sha'bi forces of Iraq reserve the right to retaliate and give [proportionate] response to the recent big crime of Americans according to international laws and conventions,” the IRGC said Monday, per Iranian state-run media.

U.S. officials blamed Iran and Kataib Hezbollah for a rocket barrage targeting an Iraqi military base that left one American civilian contractor dead and several U.S. soldiers wounded. That incident was the 11th attack on “Iraqi bases that host coalition forces in just the last two months,” according to the State Department.

“And so, it's very important that we not tolerate that kind of behavior, because if we don't respond, it will invite further aggression,” a second senior State Department official told reporters. “President Trump directed our forces to respond in a way the Iranian regime will understand. And, this is the language they speak.”

Officials have not yet released the name of the contractor who was killed.