US President Donald Trump has threatened severe sanctions against Iraq after its parliament called on US troops to leave the country.
Tensions are high after the US assassinated Iranian General Qasem Soleimani in Baghdad last week.
Iran has vowed “severe revenge”.
Soleimani, 62, spearheaded Iranian military operations in the Middle East, and was regarded as a terrorist by the US.
The general’s remains have now returned to his home country, where mourners packed the streets of Tehran early on Monday.
The new head of Iran’s Quds force – which Soleimani led – has vowed to expel the US from the Middle East.
The strike that killed Soleimani also claimed the life of Abu Mahdi al-Muhandis, a top Iraqi military figure who commanded the Iranian-backed Kataib Hezbollah group.