Another US official said that there was no change in operations at the Al Udeid Air Base in Qatar, the largest US military base in the Middle East, and that no evacuation order had been issued for employees or families linked to the US Embassy in Qatar, which was operating as usual.

US embassies across the Middle East are preparing to send home non-essential staff and families amid rising tension in the region. President Donald Trump said US personnel were being moved out of the Middle East because "it could be a dangerous place.

The price of oil initially increased more than 4% when news of the US evacuation broke, in anticipation of regional insecurity potentially leading to supply problems. Around 2,500 US troops are based in Iraq, according to the defence department.