Pentagon officials said they are worried that a key Iraqi oil refinery held by Iraqi commandos could fall to Islamic State control in the coming days.

For weeks, U.S. military officials have said that control of the refinery outside the northern city of Beiji has been bitterly contested between Iraqi forces and Islamic State militants, who have long held nearby towns.

But Islamic State fighters have made inroads in recent days, reinforcing their positions around the refinery following their loss of Tikrit to an Iraqi force backed by U.S. airstrikes, according to U.S. and Iraqi officials. […]