In a call with Prime Minister Mohammed Shia al-Sudani, Rubio "reiterated the importance of the Iraqi government taking all possible measures to safeguard US diplomatic personnel and facilities," State Department spokesman Tommy Pigott said.

Rubio also "strongly condemned terrorist attacks by Iran and Iran-aligned terrorist militia groups in Iraq, including in the Iraq Kurdistan Region," Pigott said.

Iran has carried out strikes on Kurdish Iranian militants in Iraq, after President Donald Trump said he would back an offensive by the groups into Iran.

Trump later backtracked and said he did not support a Kurdish offensive.

Iran holds influence in Iraq, which shares with its neighbor a Shia majority, and protesters have tried to storm the Green Zone which is home to the US and other embassies as well as key government buildings.

Authorities last week accused demonstrators of firing live rounds that wounded security personnel guarding the area.

In recent weeks, Trump has been warning Iraqi leaders against replacing Sudani with Nouri al-Maliki, who has a close relationship with Iran.

Maliki, a former prime minister whose relationship deteriorated with Washington during the Iraq war, earlier told AFP that he would not withdraw his nomination.