The United States is reminding its Syrian Kurdish allies not to get overly ambitious while at the same time trying to allay concerns Washington will abandon them to Turkey or a possibly resurgent Islamic State terror group.

Kurdish fighters, under the umbrella of the U.S.-backed Syrian Democratic Forces, played a key role in the collapse of the IS caliphate in Syria and continue to help administer large swaths of territory liberated form the terror group.

But Ambassador James Jeffrey, the U.S. special representative for Syria engagement and the special envoy to the global coalition to defeat IS, said Wednesday that there would not be an independent Kurdish state in Syria.

“We don’t have a political future that we offer for them,” Jeffrey told members of the House Foreign Affairs Committee when questioned about what comes next.

“The political future we offer for them is the political future we offer for everybody in Syria … a democratic, peaceful government,” Jeffrey added.

Autonomous area

Following Syria’s descent into civil war in 2011, Syrian Kurds quickly carved out an autonomous area covering much of the country’s northeast, initially sparking hopes among some that it could serve as a basis for an independent state.

But even talks of such ambitions have upset Turkey, also a key U.S. ally, which views the main Syrian Kurdish YPG militia as a terrorist organization with links to Kurdish terrorists in Turkey.

More than once, Turkish President Recep Tayyip Erdogan has threatened to strike the group to protect Turkish interests.

“Turkey has a very legitimate concern,” Jeffrey told lawmakers, though he assured them U.S. President Donald Trump remained committed to honoring both alliances.

“We are concerned about the relationship between Turkey and our SDF partners in the northeast, which is why we’re this discussion or negotiation with the Turks on a safe zone,” he added.

The U.S., Turkey and Kurdish-led authorities have been discussing the possibility of setting up a safe zone along the Turkish-Syrian border for months.

Jeffrey said Turkish officials have requested a safe zone extending for 30 kilometers, though he called that unlikely.

“We’re going back and forth with them on how deep the safe zone will be,” he said. “The idea would be that the YPG forces would withdraw and leave local forces and Turkey and the United States to figure out what we would do in the safe zone.”

Danger for Kurds

Some lawmakers expressed concerns that Trump’s plans to pull all or most of U.S. ground forces from Syria would put Washington’s Kurdish allies at risk.

“One of the reasons that I think it’s a terrible mistake is because we have had the Kurds fighting side by side with us as our loyal and faithful allies and friends,” said House Foreign Affairs Committee Chairman Eliot Engel, D-N.Y. “They’ve absorbed lots of casualties, prevented Americans from being killed.”

U.S. officials have long said the primary goal in Syria is to deal IS a lasting defeat, but Washington has also been pushing for all Iranian forces to leave the country, as well as for a negotiated end to the Syrian civil war.

In recent days, the U.S. has also raised concerns about the Syrian government’s use of chemical weapons.

The U.S. State Department said Tuesday that it was investigating an alleged attack using chlorine gas on May 19 near the northwestern city of Idlib.

“So far we cannot confirm it, but we are watching it,” Jeffrey said Wednesday.

The U.S., Britain and France launched airstrikes against Syrian government targets last April, citing “incontrovertible” evidence the Assad government had used chemical weapons against its own citizens.