"We can't tolerate the threats to our people, our men and women serving abroad," David Schenker, assistant secretary of state, for near Eastern affairs, told reporters.

Schenker did not confirm or deny a reported US threat to withdraw its troop and close its embassy in Baghdad unless the attacks against them stop.

"We are working, and we look forward to continuing to work with our Iraqi partners to keep our personnel and our facility safe," he said.

Several political and diplomatic sources have told AFP that US Secretary of State Mike Pompeo issued an ultimatum last week that all US personnel would leave Iraq unless the government puts a stop to a rash of attacks against them.

On Monday a wayward rocket targeting American troops killed seven civilians near Baghdad -- one of around 40 attacks targeting US interests since early August.

Iraq said Monday it was "not happy" with the reported pullout threat.

A US withdrawal could lead to further pullouts by members of the US-led coalition fighting holdout jihadists, which would be "dangerous, because the Islamic State group threatens not only Iraq but the whole region," Iraqi Foreign Minister Fuad Hussein said.

Iraq has long been caught in a tug-of-war between its allies Iran and the US, rendered rockier by Washington's "maximum pressure" policy against Tehran since 2018.

On Wednesday evening several rockets fell in Iraq's autonomous Kurdish region in the environs of a base used by the Democratic Party of Iranian Kurdistan, a commander for that group said.

Kurdish Iraqi authorities pinned the blame on the Hashed al-Shaabi, an Iraqi state-sponsored paramilitary network dominated by pro-Iran forces.

"The single biggest problem in Iraq is the Iranian-backed militias that are undermining stability there, and attacking the United States," Schenker said.

"The arms are not under the control of the central government. Groups continue to launch rockets at our embassy, attack Americans," he said.