Washington: Turkey needs to “do more” to assist the US-led international coalition fighting Daesh in Syria and Iraq, Defence Secretary Ashton Carter said on Thursday, urging America’s sometimes reluctant Nato partner to take steps to participate in air strikes and better control its border.

Carter said the US appreciates Turkey’s recent decision to permit US warplanes to fly combat missions out of Turkish airbases. But he said top US leaders are in “active discussions” with Turkey about the need to better stem the flow of Islamist militants crossing its border into Iraq and Syria

“This needs to be done. It’s overdue, because it’s a year into the campaign. But they’re indicating some considerable effort now, including some — allowing us to use their airfields,” he told a Pentagon news conference. “That’s important, but it’s not enough.”

He said militant fighters and supplies are making their way across the long border, and as a fellow Nato member and a neighbour to the conflict in Syria and Iraq, Turkey must police it “more than it has been controlled over the last year.”

Earlier this month the US began flying armed drones out of Incirlik Air Base and less than two weeks later F-16 fighter jets flew their first manned strike missions from the base. The stepped-up campaign adds an element of greater risk to pilots who might encounter Syrian or other air defences.

Pentagon officials had long been in talks with Turkey over the use of Incirlik, which provides much greater proximity to Daesh targets in northern Syria.

Most US aerial combat missions over Iraq and Syria are being flown from more distant airbases in Qatar and elsewhere in the Gulf region, although the US also is flying F-16s from Muwaffaq Salti airbase in Jordan. Officials have said that the F-16s could also be used to fly missions into Iraq.

There have been lingering concerns, however, that Turkey would continue to focus its military forces on Kurdish rebels, and not spend enough effort battling Daesh.

The US has said Turkey has a right to defend itself against the Kurdistan Workers Party, or PKK, which Washington, like Turkey, considers a terrorist group. The PKK is affiliated with, but separate from, Syrian Kurdish fighters allied with the United States in its fight against the Daesh group. Turkish officials say the Syrian Kurdish group is not a target of Turkey’s operations.

For the last month or so, US officials have said that Turkey is working to integrate its military into the ongoing coalition air campaign, which includes formally building Turkish strike aircraft into the daily flight operations.

Carter told reporters that he doesn’t think Turkey is dragging its feet. “We’re working through the practicalities,” he said.