Istanbul: Syrian rebel commanders say they are disappointed in the Trump administration's decision to end a covert CIA weapons and training program for opposition fighters, an initiative that began under president Barack Obama but that fizzled out amid battlefield losses and concerns about extremism within rebel ranks.

"We definitely feel betrayed," said General Tlass al-Salameh of Osoud al-Sharqiya (Eastern Lions), a group affiliated with the Free Syrian Army. Salameh and his deputies say they have received CIA support to rout Islamic State from areas of eastern Syria but that they have also fought battles against pro-government forces.

Syrian Internal Security Forces receive weapons during their graduation ceremony, at Ain Issa desert base, in Raqqa on Thursday. Some 250 residents of Raqqa are the latest batch to graduate from a brief US-training course. Credit:AP

"It feels like we are being abandoned at a very difficult moment," Salameh said. "It feels like they only wanted to help when we were fighting [IS]. Now that we are also fighting the regime, the Americans want to withdraw."

The news infuriated Republican senator John McCain, a day after he was diagnosed with an aggressive brain cancer. He branded the move "irresponsible, short-sighted" and one that "plays into Russia, Assad's hands".