WASHINGTON — US Defense Secretary Ash Carter today offered reassurances Turkey's alliance with the US and NATO, and Turkey's commitment to counter-Islamic State fight, are all still strong following a failed military coup. But experts believe that the relationship between Ankara and Washington is now in a fragile state, which could boil over into the fight against the militant group, commonly known as ISIS or ISIL.

Speaking to reporters Wednesday following a counter-ISIS coalition meeting at Joint Base Andrews in Maryland, Carter affirmed the relationship between the two nations, which plays a key role in the US-led war to oust the Islamic State from Iraq and Syria.

Dozens of top military officials from allied nations attended the meeting, with the notable exception of Turkish Defense Minister Fikri Işık, who after a late pull out held a phone conversation with Carter earlier this week.

The purpose of the call was for Carter to tell Isik "I was glad he was safe and that his ministry was functioning, which he assured me that it was, and obviously to tell him I had been concerned for him and we support the democratically elected government of Turkey," Carter said. "He assured me first, very clearly, that nothing that happened over the weekend will interrupt their support for our collective counter-ISIL campaign."

Though counter-coup purges of Turkish institutions have fueled debate over Turkey's future as a NATO ally, Carter sought to put the question to rest, saying there was no indication Turkey's relationship with the West was changed.

"Turkey has been a strong ally for decades, as we've faced together a great variety of problems, from the Cold War to today's counter-ISIL campaign," Carter said. "The alliance is very strong and our relationship's very strong."

But despite Carter's remarks, analysts say the crisis in Turkey threatens to unravel US-Turkey relations, as Turkish President Recep Tayyip Erdogan links the US alliance to the extradition of his old enemy, Fethullah Gulen, an Islamic preacher who lives in exile in Pennsylvania.

Ankara's pressure on Washington to extradite Gulen, whose supporters Turkey has blamed for the attempted coup, has fueled speculation that US access to the Incirlik Air Base in southern Turkey, a key launch pad for the projection of US power into Syria, Iraq and beyond, could be at risk.

"It's way beyond Incirlik, it's the entire US-NATO-Turkey relationship, the entire collaboration in Syria," said Michael O'Hanlon, a senior fellow in Foreign Policy at the Brookings Institution. "Everything is potentially at risk, and there's no way to know because it's only going to be in Ergodan's brain, when he decides to stop pushing, because we're probably not going to extradite Gullen. All issues are on the table, even the basic alliance, even Turkey's membership in NATO."

At a joint news conference with European Union foreign policy chief Federica Mogherini, US Secretary of State John Kerry had warned that Turkey could run afoul of NATO's "requirement with respect to democracy," if it fails to uphold the rule of law in the wake of an attempted coup. The comment came amid a crackdown and mass firing of soldiers, police, judges, teachers, government staff, clerics and intelligence officials reported Wednesday to number above 50,000 people.

On Monday, Kerry said that Turkey must provide evidence of Gulen's involvement in Friday's coup attempt if the US is to extradite him, and by Tuesday the State Department confirmed Turkey had sent it related materials, which the US plans to review. For his part, Gulen told reporters Monday he condemned the attempted coup.

One Turkish analyst painted a dire picture of the divide on Gulen.

"The United States is refusing to extradite someone the Turkish government considers as dangerous as Osama bin Laden," said Ömer Taşpınar, Turkey and Middle East expert at the Brookings Institution. "This could go very far, and the Turkish government could react very irrationally. This is literally an existential problem for the Turkish government. Erdogan escaped a coup and an assassination attempt, and he is a wounded tiger, and he will extract revenge."

Inside Turkey, an anti-American backlash has already started, including statements from Turkish officials blaming the US and questioning Kerry's initial statement about about the coup attempt, which could be read as ambiguous, said Eric Edelman, former US ambassador to Turkey and former undersecretary of defense for policy. He described Kerry and the Obama administration as "badly stung by the level of anti-american rhetoric."

"We are in for a very bumpy period in US-Turkey relations," Edelman said on a conference call to discuss the crisis, which was hosted by the Jewish Institute for National Security Affairs. "The bar to extradite Gulen needs to be very high, and if we don't return him, I think we can count on some problems, perhaps threats of loss of access to Incirlik."

Following the coup attempt, air space above Incirlik was closed temporarily and the base commander arrested for complicity in the failed coup, "but it also sent a message that access to Incirlik is something the government grants us, not a right," Edelman said.

The US has alternatives to conduct the air war against the Islamic State, O'Hanlon noted, with facilities available in Kuwait, Bahrain, Qatar, Italy and aircraft carriers. He said Incirlik itself is not irreplaceable.

"All of these [alternatives] involve flying several hundred miles instead of several dozen miles to the battlefield and that's not good, but it's still less than an hour and we can do it," O'Hanlon said.

Edelman and Michael Rubin, a former Pentagon official and Middle East scholar with the American Enterprise Institute, suggested the US government seek such alternatives. Rubin called Turkey's calls for Gulen's extradition "blackmail" and called for a hard line against it and the counter-coup's targeting of teachers and reporters.

"Weakness never brings peace, and if Turkey were a real ally, instead of Pakistan on the Mediterranean, it wouldn't be trying to undercut or hamper the fight against the Islamic State," Rubin said.

Still, the US relies on Turkey "enormously" in the ground war, and potentially large operations that could figure in the end-game in Syria, O'Hanlon said. Turkish cooperation would be pivotal in any plans to create safe zones inside Syria, an idea championed by Hillary Clinton, the Democratic presidential candidate and former secretary of state, and David Petraeus, the retired four-star general and CIA director.

US success also depends on greater collaboration with Turkey with respect to ongoing covert actions inside Syria. The US reportedly has 300 US Special Operations forces in Syria aimed at expanding the numbers of Arab fighters battling the Islamic State, efforts that hinge on Turkish help.

"When you try to access specific insurgent groups, especially in northern Syria, you rely on Turkey," O'Hanlon said.

Turkey provides materiel, financial and intelligence support to forces directly fighting the Syrian government—including Islamist forces, according to Christopher Kozak, research analyst at the Institute for the Study of War. That support has included weapons, equipment and freedom of movement.

One short-term side effect of the counter-coup is that while Erdogan focuses on purging Turkey's military and intelligence organizations, it should grant an opportunity for forces loyal to the Syrian government to expand their terrain in Aleppo, and for Kurdish forces Turkey opposes to gain ground.

For now, the Turkish military looks to be in disarray, which damages its ability to fight the Islamic State, whatever the relationship with the West.

A third of its general officer corps, 125 people have been arrested on suspicion of coup plotting, and that purges have reportedly left Turkey's F-16 force without pilots. The commanders who remain will be more focused on disloyalty than military readiness, according to one analyst on the Jewish Institute for National Security Affairs call.

"This is going to emerge as a damaged military, far less capable of helping us in the anti-ISIL fight," said Svante Cornell, a Central-Asia scholar at the Johns Hopkins School of Advanced International Studies.

Aaron Mehta in Washington contributed to this report.

Twitter: @ReporterJoe