U.S. Defense Secretary Ash Carter is convening his final war-planning conference with core members of the anti-Islamic State coalition, dogged by questions about what Donald Trump's arrival in the White House next month will mean for the future of the coalition.

Closing out a nearly two-week overseas trip that included a stop in Iraq, Carter was meeting Thursday with his counterparts from 14 nations. They are to receive an update from Army Gen. Joseph Votel on the battles to retake Mosul, the Islamic State's key stronghold in Iraq, and Raqqa, the self-declared IS capital in Syria. As head of U.S. Central Command, Votel is the top officer overseeing the counter-IS campaign in Syria and Iraq.

The defense officials also will discuss doing more to train and equip the kinds of local Iraq and Syrian forces, including police and tribal fighters, that will be needed to hold Mosul and Raqqa once, as expected, the Islamic State is uprooted from those cities. IS has held those centers for more than two years.

But the backdrop to these discussions is deep uncertainty in London, Berlin and other coalition capitals about the implications for the counter-IS efforts of a change in U.S. administrations in January. Trump has criticized President Barack Obama's approach to fighting the militant group as weak and ineffective, and he has suggested that the U.S. has blindly supported anti-IS groups without knowing their true aims.

Among the questions Carter cannot answer: Will Trump withdraw support for U.S.-backed rebels groups in Syria, who have now lost the city of Aleppo? And if he does, will he join forces with Russia? How might such moves affect public support for the anti-IS coalition in Germany and elsewhere?

Though Obama has tried to work diplomatically with Russia, Syria cease-fire deals have repeatedly collapsed, with the U.S. accusing Moscow of failing to use its influence to prevent Syria's President Bashar Assad from violating them. Meanwhile, Russia's military intervention has succeeded in helping Assad reclaim the upper hand. The U.S.-led coalition has avoided direct military action against Assad's force, focusing instead on supporting local rebels willing to fight the Islamic State group while coupling that effort with aerial bombing in both Syria and Iraq.

Carter is expected to emphasize to his counterparts at the London conference the prominent role that retired Marine Gen. James Mattis will play as the president-elect's choice to succeed Carter at the Pentagon. Mattis is well-known in Europe, having headed NATO's Supreme Allied Command Transformation from 2007 to 2009, a role focused on preparing the military alliance for security challenges of the future.

Carter has held five other counter-IS conferences with coalition partners. Thursday's will be the first to include Iraq's army chief of staff, Lt. Gen. Othman al-Ghanami. The other countries represented, in addition to the U.S., are Australia, New Zealand, Belgium, the Netherlands, Canada, Denmark, France, Germany, Italy, Britain, Norway, Spain and Turkey.

In addition to hearing from Votel about the military campaigns in Iraq and Syria, the officials will receive a briefing by Marine Lt. Gen. Joseph Osterman on U.S. efforts to disrupt the Islamic State group's plans for directing, supporting and inspiring attacks outside of Iraq and Syria. Osterman is deputy commander of U.S. Special Operations Command.

At nearly every stop on his current round-the-world tour, Carter has met with U.S. troops and assured them that the counter-IS campaigns are going according to plan. At Aviano air base in Italy on Wednesday, Carter said coalition-backed Arab and Kurdish fighters are within 15 miles of Raqqa, the self-declared IS capital in Syria, and that they are "completing the envelopment and ultimately the seizure" of the city.

He also alluded to the uncertain future of the campaign and the coalition.

"We need to look ahead," he said. "What comes after? And are we getting ready for that?"