Gen. Mazloum Abdi briefed journalists in Washington on Thursday about the U.S.-backed forces’ operations alongside coalition allies to prevent a resurgence of the Islamic State terror group, which once controlled vast sections of Iraq and Syria and held millions under its brutal rule.

The airstrikes from Turkey, which has long battled a domestic Kurdish separatist movement and considers the SDF terrorists, have hindered the SDF’s ability to fight ISIS, the general said. Gen. Abdi also accused Turkey of trying to financially cripple his movement.

“Most of the income from our budget comes from the oil that we have here,” he said. “Since all these locations were hit by the Turks, we lost more than half of the budget that we depend on.”

On Thursday, a Pentagon spokesman said the U.S. was not aware of the reports that Turkey had attacked civilian infrastructure in the area controlled by the SDF and declined to comment about the long-simmering tensions between Turkey, a key NATO ally, and the SDF.

The Biden administration is expected to allow Turkey to buy dozens of F-16 jet fighters in exchange for ending its opposition to Sweden’s bid for NATO membership. Gen. Abdi said he is worried that Ankara will use the warplanes to attack his troops.

Sen. Chris Van Hollen, Maryland Democrat, said while he was “deeply troubled” by Turkish President Recep Tayyip Erdogan’s attacks against the SDF, he wouldn’t try to block the F-16 sale.

“The administration assured me that they continue to voice their strong objections to these attacks, including the threat posed to U.S. forces working with the SDF, and reaffirmed their ongoing commitment to supporting this crucial partner, who has served as the tip of the spear in our campaign to defeat the Islamic State,” he said in a statement last week.

“It is clear that we must keep a close watch on Turkey in the weeks and months ahead. Actions speak louder than words,” Mr. Van Hollen said.

The short-term goal for ISIS leadership is to free their fighters held in SDF-run prison in Syria. After that, the jihadi group plans to consolidate and take back control of the areas they once held, Gen. Abdi said.

He warned that escalating attacks in the Middle East by Iranian-backed militia groups are also providing an opportunity for the Islamic State to rebuild its strength. The Pentagon keeps a deployment of about 900 U.S. troops in Syria as part of the anti-ISIS campaign, but those troops have become the target for attacks by Iran-aligned militia groups in both Iraq and Syria.

“The main goal behind the attacks on our joint bases … is to force the United States and the coalition force to withdraw from Syria,” Gen. Abdi said from Syria in a video conference. “These attacks and growing challenges further complicate the battle against ISIS.”

About 10,000 ISIS fighters are held in several SDF-run prisons and detention camps in northeastern Syria. Gen. Abdi said the prisoners are aware of the continuing attacks launched against U.S. forces by Iran-backed militias.

“Hope from them is growing every day by seeing all this tension around them. They see hope,” he said.

Gen. Abdi said his forces are continuing to launch successful operations against ISIS, with one glaring exception.

“We have not been successful in reaching out to the areas under Turkish control to take out these [ISIS] leaders,” he said.