Getty A US dilemma: Kurds or Turks? Syrian Kurds are serving as “boots on the ground” against the Islamic State, but Turkey opposes their involvement.

As the United States and Turkey prepare to launch airstrikes to oust the Islamic State from a stretch of northern Syria, they appear at odds over the role of a critical fighting force on the ground: the Syrian Kurds.

Turkey insists that the main Syrian Kurdish militia have no role in the upcoming operation, a reflection of its worries about the separatist leanings of Kurds in the region. But U.S. officials aren’t willing — at least not publicly — to freeze out the Syrian Kurds, whose fighters already have driven the Islamic State, also known as ISIS or ISIL, out of much of northern Syria.

“Our airstrikes are to support the anti-ISIL efforts of anti-ISIL forces in that area, which include Syrian Kurds, Arabs and Turkmen,” a State Department official said, sidestepping questions about whether the U.S. has privately told the Syrian Kurds to stay out of the operation.

The Obama administration’s careful messaging comes amid a growing sense in U.S. foreign policy circles that America needs to re-calibrate its approach to the Kurds, an ethnic group without a homeland that has become a pivotal player in the Middle East. It also comes as Turkey clashes with separatist Kurds on its own soil — an escalating battle some fear could undermine U.S.-Kurdish ties and, by extension, the fight against ISIL.

“The U.S. needs some sort of better system for addressing the Kurds and seeing the Kurds as a separate group with interests that don’t always align with the states in which they live,” said Aliza Marcus, author of “Blood and Belief: The PKK and the Kurdish Fight for Independence.”

Observers describe Turkey as being reluctant to take on the Islamic State, only recently permitting the U.S. to use its soil to launch airstrikes against the Sunni extremists. (The two countries are still publicly differing over whether the upcoming operation will create a “safe zone” as Turkey wants or something less defined as the U.S. prefers). The Kurds, on the other hand, have been the “boots on the ground” vital to defeating the jihadists, who have grabbed territory in both Iraq and Syria.

Over the decades, Kurdish aspirations for a state have been brushed aside by world powers, including the United States.

“The issue with Turkey, I think, is going to force the U.S. to come to clarity on how much it values the Kurds and whether it’s going to have a separate Kurdish policy,” said Blaise Misztal, director of the national security program at the Bipartisan Policy Center.

The U.S.-Kurdish relationship is complicated in part because the Kurds are not monolithic. Their 30 million-strong community is spread over the territories of Iran, Iraq, Syria and Turkey, and it has its own factions and internal rivalries. Over the decades, Kurdish aspirations for a state have been brushed aside by world powers, including the United States.

U.S. diplomacy has traditionally focused on managing relationships between central governments, which has hampered the ability — or even willingness — to look at the Kurdish issue beyond the lens of national capitals.

There’s no single person in charge of Kurdish policy at the State Department, for example, or even a working group. Also adding to the bureaucratic tangle is that Turkey, a NATO member that has had aspirations to join the European Union, is handled by the State Department’s Europe bureau, while most of the big issues related to the Kurds are dealt with by the Middle East division.

One reason for the fractured approach to the Kurds is to avoid angering the Turkey and Iraq, which could read changes to the U.S. government infrastructure as signaling support for a Kurdish state.

Henri Barkey, a former State Department official now with the Woodrow Wilson International Center for Scholars, said establishing an office to deal with the Kurds is less important than training America's foreign policy bureaucracy to remember them in the first place.

“We do need to think about them seriously and not be surprised and understand what impact they have in all the countries in the region,” Barkey said. “Instinctively we know this. But the way we look at them is they’re a factor from the perspective of Turkey, Iraq. We don’t understand what it is that drives the Kurds.”

The battle against the Islamic State has certainly raised the importance of the Kurds to U.S. national security. While U.S. presidential candidates have all discussed the need to defeat the Islamic State, few have focused extensively on the Kurds, though some have backed legislation to directly arm Kurdish fighters in Iraq, as opposed to routing weapons through Baghdad. Kentucky GOP Sen. Rand Paul has gone further than most in arguing the Kurds deserve their own country.

Iraqi Kurds are the most well-established of the various Kurdish factions: they have a regional government and significant autonomy, an outgrowth of the 2003 U.S. invasion of Iraq. Their armed forces, known as thepeshmerga, have fought well against the Islamic State, aided by U.S. air power.

Syrian Kurds have managed to carve out their own space amid the Syrian civil war while also proving adept against the Islamic State. The main armed group defending the Syrian Kurds is known as the YPG, while its political affiliate is the PYD. Those ground forces, too, have been aided by U.S. airstrikes.

Roughly half of all Kurds live in Turkey, where they have long faced repression. Separatist Kurds in Turkey are led by the PKK, which launched an armed resistance in 1984 and is listed as a terrorist group by the United States.

In 2013, the PKK and Turkey agreed to a cease-fire, but it eroded as the months wore on. In July, a suicide bombing blamed on the Islamic State killed 32 people in a Kurdish-majority town, leading Kurdish groups to accuse Ankara of not doing enough to stop the flow of Islamic State fighters. After the bombing, a PKK-linked group claimed the killing of two police officers, prompting Ankara to launch a bombing campaign against PKK hideouts in southeast Turkey and in northern Iraq.

The United States has strongly supported Turkey’s right to attack the PKK, blaming the Kurdish group for the breakdown of the cease-fire. But that strident support for Turkey could fray America’s growing relationship with the Kurds in Syria.

That’s because the PKK has strong links to the Syrian Kurds. PKK fighters also have directly battled the Islamic State, according to experts and reports from the region.

PKK and Syrian Kurdish fighters “are interchangeable, depending on where it is that they are fighting,” said Aaron Stein, a non-resident fellow with the Atlantic Council. He and others warned that if Turkey keeps up its fight against the PKK, it could weaken Kurdish forces battling the Islamic State in Syria in part by drawing some of the fighters to Turkey.

A Turkish diplomatic source said the Syrian Kurds should “act more responsibly” and cut off their ties to the PKK.

“The longer Washington appears to back Turkey’s counter-PKK campaign, the more we will see tension between the U.S. and the YPG, its most effective ally on the ground against the Islamic State,” added Jonathan Schanzer, a Middle East expert with the Foundation for Defense of Democracies.

A Turkish diplomatic source said the Syrian Kurds should “act more responsibly” and cut off their ties to the PKK. He alleged the Syrian Kurds are “are changing the demographics and intimidating the population” in enclaves they control. He also defended Turkey’s overall role in the battle against the Islamic State.

Mehmet Yuksel, a Kurdish official based in Washington, said Turkish President Recep Tayyip Erdogan is fulfilling multiple goals by going after the PKK while simultaneously working with the U.S. on the operation against the Islamic State.

He can prevent the Syrian Kurds from taking more territory and creating a contiguous region under Kurdish rule. He can weaken political support for the HDP, a pro-Kurdish political party in Turkey whose strong showing in June’s parliamentary elections helped deny Erdogan’s party an outright majority. And he can chip away at the U.S. relationship with the Syrian Kurds, argued Yuksel.

“If there’s an intensification of the conflict [with the PKK] — and the United States has to respect the relations with Turkey — in that case the Kurdish people will ask ‘We are the only ones which is staying against ISIS and at the same time fighting against ISIS for all of humanity — why is United States leaving us alone in the fight?’” said Yuksel, who represents the HDP.

When asked if the U.S. feared that the Turkish strikes on the PKK could damage American relations with Syrian Kurds, a State Department official replied: “Turkey has said it has no policy or plans for operations aimed at the PYD/YPG.”

Michael Werz, a senior fellow with the Center for American Progress, suggested that U.S. officials raise the idea of a roadmap to peace between Turkey and the Kurdish separatists, one that dangles the idea of taking the PKK off the terrorism list several years from now. Because of American air support for Kurdish fighters — be they PKK or YPG — battling ISIS, “I think the U.S. has for first time has substantial leverage over the PKK,” Werz said.

One reason the U.S. should get more involved in the Turkey-PKK tangle is growing worries about Turkey’s political and social stability, Werz said.

Turkey is technically a secular democracy, but Erdogan, who has Islamist roots, has exhibited authoritarian leanings and wants to expand the presidency’s powers. Just this week, he called for new elections in November after the various parties who won seats in June couldn’t form a government.