The US says it is sending a warship into the Gulf to provide President Obama with military options should the situation in Iraq deteriorate further.
US Defence Secretary Chuck Hagel ordered the USS George HW Bush, which carries dozens of fighter jets, to be moved from the North Arabian Sea to the Gulf.
The aircraft carrier will be accompanied by the guided-missile cruiser USS Philippine Sea and the guided-missile destroyer USS Truxtun. They were due to arrive in the Gulf late on Saturday.