U.S. Defense Secretary Ash Carter said Thursday Turkey needs to do more to fight Islamic State and control its borders.
Carter said Turkey has agreed in principle to join the U.S.-led airstrikes against the militants, but said it is only part of what the Turks need to do.
"We need them also as a neighbor to this conflict zone, as a longtime NATO ally and a responsible member of the anti-ISIL coalition to control...the long border that they have with both Syria and Iraq, more than it has been controlled over the last year," Carter said.
Islamic State fighters and equipment have been able to cross into Iraq and Syria from Turkey.
The secretary said he does not think the Turks are "dragging their feet," but said their increased participation, including joining the airstrikes, is "overdue."
"It's a year into the campaign, but they're indicating some considerable effort now, including allowing us to use their airfields. That's important, but not enough."
Carter said President Barack Obama has also been part of the active discussions with Turkey to get more involved.
Turkey agreed last month to allow U.S. jets attacking Islamic State to use Incirlik Air Base, but has focused its increased military participation in the region on its own long-running fight against Kurdish guerrillas.
U.S. intelligence says even after a year of the U.S. bombing campaign and some success on the ground by Iraqi forces, Islamic State is no weaker today than last September.
Carter refused Thursday to characterize the situation as a "stalemate." He said he is confident Islamic state will be defeated and that the U.S. is using the right strategy.
But he said the fight is complicated and hard work.