(Adds background on Obama weighing options, ship)
WASHINGTON, June 14 (Reuters) - U.S. Defense Secretary Chuck Hagel ordered an aircraft carrier moved into the Gulf on Saturday, readying it in case Washington decides to pursue a military option after insurgents overwhelmed a string of Iraqi cities this week and threatened Baghdad.
"The order will provide the Commander-in-Chief additional flexibility should military options be required to protect American lives, citizens and interests in Iraq," the Pentagon said in a statement.
The carrier USS George H.W. Bush, moving from the North Arabian Sea, will be accompanied by the guided-missile cruiser USS Philippine Sea and the guided-missile destroyer USS Truxtun, the statement said. It added the ships were expected to complete their transit into the Gulf later on Saturday.
President Barack Obama said on Friday he needed several days to determine how the United States would help Iraq deal with the insurgency. But he ruled out sending U.S. troops back into combat and said any intervention would be contingent on Iraqi leaders becoming more involved.
The Pentagon is preparing a range of options for Obama, including air strikes. Such actions would be aimed at helping Iraq counter militants of the Islamic State in Iraq and the Levant, or ISIL.
The USS George H.W. Bush is a Nimitz-class aircraft carrier, the largest warships in the world, according to the U.S. Navy. The ships are powered by two nuclear reactors and can carry a crew of about 6,000 people.
(Reporting by Missy Ryan; Editing by Eric Beech and Frances Kerry)