WASHINGTON - The USS Mesa Verde with 550 Marines on board entered the Gulf on Monday to support possible US action to help Iraq's Shi'ite-led government combat a Sunni Islamist insurgency that has overtaken large areas of the country's north, CNN reported.

The USS Mesa Verde joins the aircraft carrier USS George H.W. Bush, which the Pentagon ordered on Saturday to move into the Gulf. President Barack Obama has said he is considering military action, short of putting US troops in Iraq, to aid that government's efforts to stop the insurgency.

Islamist fighters vow to capture Baghdad