The United States has told embassy staff in Iraq to evacuate amid fears Israel could be poised to strike Iran within days, regardless of American support.

Non-essential US embassy staff in Baghdad are set to leave due to heightened security risks, US government sources have warned without elaborating.

President Donald Trump told media on Wednesday that 'they are being moved out because it could be a dangerous place and we'll see what happens'.

Asked why family members of military personnel were allowed to voluntarily leave the region, he ominously replied: 'You'll have to see.'

White House spokesperson Anna Kelly said that the decision was taken 'as a result of a recent review' by the State Department, without mentioning a possible attack.