The U.S. military says the Pentagon is open to sending additional troops to Iraq if needed to meet specific requirements of the Iraqi security forces as the fight against Islamic State militants continues.

Air Force Col. Pat Ryder, spokesman for U.S. Central Command, said the military is keeping its options open. He says more troops may be needed as the battle for the key city of Mosul moves ahead. Any decision would require presidential approval.

Defense Secretary Ash Carter announced in Iraq on Monday that the U.S. will deploy 560 more troops to the war to help set up a logistics base at an airfield south of Mosul. That would bring the U.S. troop authorization in Iraq to 4,647.

Ryder says there currently are nearly 3,700 U.S. troops in Iraq.