WASHINGTON?International military and diplomatic leaders gathering in Washington this week to review the fight against Islamic State will meet under a cloud of uncertainty after the surprise coup attempt in Turkey.
Turkey's foreign minister is among those slated to attend. Turkey is central to the U.S.-led fight against the militants, but has ratcheted up tensions with Washington over a demand to extradite Fethullah Gulen, a cleric living in Pennsylvania who has been blamed by Ankara for the coup. Mr. Gulen has denied playing a role.
The U.S.-led coalition relies on Incirlik Air Base in southeastern Turkey, about 60 miles from the Syrian border, as a key military facility in the campaign, launching many of its strikes against targets in Syria from there. Turkish officials closed the air space around the base for a time following the coup attempt, but operations have been restored, officials said.
The U.S. also worked to win Turkey's cooperation in a military campaign against Islamic State in the Syrian border city of Manbij.
The Obama administration wants to keep the Islamic State offensive on track. The administration will host foreign and defense ministers from more than 30 countries for the previously scheduled meetings at Joint Base Andrews near Washington on Wednesday and at the State Department on Thursday.
The officials will discuss how to accelerate the campaign to defeat Islamic State and will review efforts to disrupt terrorist financing, stop the flow of foreign fighters and counter the use of social media by extremist groups.
"We will come together to not only review what we are accomplishing but to self-criticize and to try to analyze what we can do better and do faster," Secretary of State John Kerry said in Brussels on Monday. "We were pleased to see that the operations at Incirlik have been restored and we are all determined to make sure that the efforts against ISIL or Daesh do not miss a beat in the days ahead," he added, using alternative terms for Islamic State.
Mr. Kerry spoke with the Turkish foreign minister, Mevlut Cavusoglu, on Monday, following three phone calls over the weekend. President Barack Obama and Defense Secretary Ash Carter haven't yet spoken with their Turkish counterparts. Turkey is a North Atlantic Treaty Organization ally.
Experts said the coup attempt is unlikely to deeply affect the day-to-day functioning of operations at Incirlik, but the events over the weekend have illustrated the fragility of a key U.S. ally in the fight against Islamic State.
"The United States will need to look at alternative basing options?not because the Turks will pull out of Incirlik, it just becomes prudent planning," said Aaron Stein, a senior fellow at the Atlantic Council think tank.
The U.S. negotiated with Turkey for months to win approval a year ago to use the base to launch strikes from Incirlik.
"It will continue to be an important part of the campaign," Pentagon spokesman Peter Cook said Monday. "We have the ability to adjust our operations in such a way that we can account for problems or delays there."
Turkey's defense minister, Fikri Isik, will not attend the meeting. Mr. Cook said he believes that other Turkish defense officials will be there.
Incirlik wouldn't be used to conduct strikes against Mosul, the largest Iraqi city controlled by Islamic State. But it is critical for strikes against Raqqa, the de facto capital of the group in Syria.
A senior NATO official said that Turkey now sees Islamic State as a threat in a way that it did not before a recent deadly attack on the Istanbul airport, so has a reason to maintain its role in the fight.
"Erdogan feels the IS threat in a way he didn't a year ago," the official said. "I don't know how he can close the door on cooperation. I don't know how he can walk away from that."
Some military and other U.S. government officials said privately they were concerned that the coup could harm U.S. operations against Islamic State, but noted that because Turkey's top generals appear to have opposed the coup the damage to the relationship could be limited.
Soner Cagaptay, a Turkey expert at the Washington Institute for Near East Policy, said as the investigation into the coup unfolds, Turkish officials could temporarily freeze Turkish military activity if they are probing military officials.
"The campaign could plateau, the campaign could suffer setbacks, I think that will be part of the conversations," Mr. Cagaptay said.
Mr. Stein, of the Atlantic Council, said U.S. officials are likely to be interested in hearing about the cohesion of the Turkish armed forces in their Washington meetings.
Julian E. Barnes
Write to Felicia Schwartz at Felicia.Schwartz@wsj.com