​In this photo released by the Turkish Presidency Press Office, Turkish President Recep Tayyip Erdogan, center, and U.S. Secretary of State John Kerry, third left, speak during a meeting in Ankara, Turkey, Sept. 12, 2014. © Turkish Presidency/AP Photo ​In this photo released by the Turkish Presidency Press Office, Turkish President Recep Tayyip Erdogan, center, and U.S. Secretary of State John Kerry, third left, speak during a…
WASHINGTON — A U.S. official on Friday acknowledged that NATO ally Turkey had complicated efforts to build a moderate Syrian rebel force by coordinating with groups, including al-Qaida’s Nusra Front, that were considered off limits by the Obama administration.The disagreements hamstrung progress on identifying and building a trusted rebel force that could fight on two fronts, against the regime of Syrian President Bashar Assad as well as against extremists from the Islamic State or Nusra Front. While Turkey in recent months has taken a harder line toward the militants, the dispute has resurfaced because the Syria leg of the strategy President Barack Obama outlined to combat the Islamic State relies heavily on an on-the-ground opposition partner, which still doesn’t exist in any viable form.

The U.S. official, who spoke on condition of anonymity because of the sensitive diplomacy involved, said “it’s no secret” that the Obama administration had been pressing Turkey for years to crack down on the flow of jihadists who entered Syria via Turkey’s porous borders. The official disputed that the Turks “worked with” Nusra directly, but he acknowledged that Ankara allowed the group operating space because it was useful in the fight against Assad.

“For quite a while, Turkey, at the very least, turned a blind eye to it,” the U.S. official said. “It’s only in recent months that they’ve done a 180 and now recognize the dangers posed by ISIS and other extremists.” ISIS is an acronym for the Islamic State.

Turkish officials did not respond to requests for comment.

Secretary of State John Kerry was in Ankara on Friday for talks with Turkish leaders about the coalition the Obama administration is assembling to fight the Islamic State, the extremist group that controls vast swaths of territory in Turkey’s neighbors, Syria and Iraq.

Kerry on Friday named retired Gen. John Allen as special envoy to the anti-extremist coalition; the State Department’s Iraq point man, Brett McGurk, will serve as his deputy. In brief remarks to journalists, Kerry swatted away questions about Turkey’s wavering, calling it “entirely premature and frankly inappropriate at this point in time to start laying out one country by one country what individual nations are going to do.”

Turkey has sent mixed signals about its willingness to take a more public position alongside the Americans. While Ankara did label the Nusra Front a terrorist organization in June, Turkish opposition figures claim that the government still isn’t doing enough to stop jihadists from using Turkey as their way station to Syria.

Turkey raised more eyebrows this week at a regional summit in Saudi Arabia, where Turkish officials declined to sign onto a communique expressing support for the campaign against the Islamic State.

But there are other complicating factors that prevent Turkey from taking too prominent a role, not least the fact that the Islamic State is holding dozens of Turkish hostages. In June, the jihadists stormed the Turkish Consulate in Mosul, Iraq, and seized 49 personnel, including the consul general. Ankara appears to be taking pains to mute its public criticism of the Islamic State for now, presumably so as not to shut the door on the hostage recovery effort.

“Turkey is a European and regional power but does not yet seem fully committed to dealing with the Islamic State,” Anthony Cordesman, a former defense official who is now with the Washington-based Center for Strategic and International Studies, wrote in a commentary this week.

“It fears any form of Kurdish separatism, has hostage issues, has major problems in securing its southern border, and does not want more of a Syrian or Iraqi crisis on its southern borders,” Cordesman wrote. “At least some elements in Turkey also seem to benefit from trade with the Islamic State and others are happy to support the Iraqi Kurds in their separatist efforts.”

The U.S. official’s confirmation of Turkey’s relations with Nusra Front comes in response to remarks by a former U.S. ambassador to Turkey, Francis Ricciardone, who described to reporters on a media call Thursday how the American side grew frustrated that “the Turks, frankly, worked with groups — for a period including al Nusra, whom we finally designated — that we were not willing to work with.”

State Department spokeswoman Marie Harf said she had no comment on Ricciardone’s remarks, emphasizing that he’s a former diplomat. Ricciardone served as the U.S. ambassador to Turkey until July; through other regional postings he has also worked closely on issues related to Iraq, Iran, Egypt and Jordan. Before Turkey, he was deputy ambassador in Afghanistan.

The State Department labeled Nusra Front a foreign terrorist organization in late 2012 — a move that garnered a backlash from some more mainstream rebels who valued the Islamists’ battlefield prowess.

In his remarks to reporters, Ricciardone described extremist rebels such as those in Nusra and the Salafist group Ahrar al Sham as “beyond the pale.” But he suggested that the Turks didn’t take the U.S. concerns seriously. Ricciardone balked at assisting an Islamist coalition that includes the ultraconservatives of Ahrar al Sham, which the U.S.-backed Syrian opposition coalition has described as moderate, because there was no telling “what might become of those weapons.”

“The short version is: We agreed to disagree on a number of specific cases,” Ricciardone said of the U.S. talks with the Turks.

Ricciardone said Obama’s speech this week suggested he was ready to “take more risks with the Syrian opposition,” because of the urgency of the Islamic State threat. That, he said, is a big change from the president’s longtime conservative approach of standing back “from engagement with all but the groups that we were most certain about, and even then we were none too certain.”

Syrian opposition-focused media picked up Ricciardone’s remarks, using them as fuel in their campaign to show that Turkish President Recep Tayyip Erdogan’s administration is too cozy with extremist elements.