Turkey says Syria using force is an option against US-backed fighters who helped defeat ISIS

The warning underscores mounting regional pressure as negotiations aimed at integrating the SDF into Syria's national army remain stalled nearly a year after a U.S.-backed framework agreement was signed.

"Fundamentally, the United States remains the SDF's biggest and most important backer, supporter, provider of finance, training and, to an extent, defense," he said.

Lister said Washington has already used significant leverage, including compelling SDF leader Mazloum Abdi to sign the March 2025 framework agreement.

"We would not have had the March framework agreement had it not been for basically Gen. Mazloum being strong-armed onto a helicopter, flown to Damascus, and told that he needed to sign that agreement," he said.

The SDF also said Turkish Bayraktar drones struck multiple SDF positions near Maskanah and Tabqah. Turkey and the Syrian government had not publicly responded to the claims.

The crisis stems from a failed March 2025 agreement intended to merge SDF forces into Syria's Ministry of Defense.

"There's no question that Damascus has been a tough negotiator," Lister said. "Having said that, the government has also bent significantly."

Lister claims the deal stalled because of internal divisions within the SDF. "The fact that no deal has been implemented is quite frankly because the SDF is not a united, cohesive movement," he said. "There are elements within the SDF who absolutely do not want this deal to be implemented."

He said some factions are deliberately delaying implementation. "Their calculation is clearly that the longer that they can stall, they hope that the Syrian transitional government will do something to destroy its international credibility," Lister said. "It's just a stall-and-wait-and-see approach."

"That approach is intrinsically dangerous," he said. "It only guarantees conflict."

"Turkey is primed to get back involved," he said. "When Turkey has gone all out on the SDF, the SDF haven't stood a chance."

According to Lister, only pressure from the highest level could alter the trajectory.

"The only thing that's going to change the equation here is if President Trump makes it publicly clear that this deal has to be made and implemented expeditiously," he said.

"This is not contained," Lister warned. "All the preparations are clearly being made for this to become an active military zone unless serious diplomacy pulls both sides off the brink."

A statement issued by the U.S. Mission of the Syrian Democratic Council accused Syria's transitional authorities of targeting Kurdish areas in Aleppo and undermining the political process. "What is happening now is not merely a military escalation by the Damascus authorities," the statement said. "It is an effort to undermine the prospects of building a new Syria."

The council said Syrian forces were taking control of Kurdish neighborhoods in Aleppo "through force, intimidation, and coercion," and warned that the escalation could destabilize the region. The group also warned that continued fighting could benefit extremist groups.

"The primary beneficiary of this escalation will be ISIS, allowing terrorism to re-emerge and once again threaten international peace and security," the statement said.

"We call for an immediate and independent investigation into the crimes committed against Kurds in Aleppo. We urge US decision-makers to monitor the conduct and behavior of the Damascus authorities, take the necessary measures to halt the escalation, and implement the March 10 agreement in full-without any delay or pretext whatsoever."

Reuters contributed to this report.