BEIRUT — A small number of U.S.-backed rebels have defected and joined government forces south of the country days after the U.S. announced an end to a CIA program that backed opposition fighters, Syrian opposition activists said Saturday.

The defection of at least four rebels came after The Washington Post reported that the White House has decided to halt the CIA supply-and-equip program for Syrian rebels.

U.S. President Donald Trump essentially confirmed the existence of the program and its cancellation Monday night when he lashed out at The Washington Post. The president tweeted that the newspaper “fabricated the facts on my ending massive, dangerous, and wasteful payments to Syrian rebels fighting (Syrian President Bashar) Assad.”

The defection also came as Col. Ryan Dillon, the spokesman for the U.S.-led coalition fighting the Islamic State group, told CNN this week that “the coalition supports only those forces committed to fighting” the Islamic State group.

The U.S. has been mainly backing the Kurdish-led Syrian Democratic Forces that have been among the most effective in fighting IS in Syria. SDF fighters are currently trying to capture the northern city of Raqqa, the de facto capital of the extremists, under the cover of airstrikes by the U.S.-led coalition.

The chief of the Britain-based Syrian Observatory for Human Rights, Rami Abdurrahman, said four members of the Revolution Commando Army defected Thursday.

Ahmad al-Masalmeh, an opposition activist based in southern Syria, and another activist with wide knowledge about U.S.-backed rebels confirmed the defections on Saturday.

“Some rebel groups were not active and did not go into battle but they were still getting assistance,” al-Masalmeh said. He added that the four defected with their weapons and joined government forces.

There was no immediate comment from Syrian authorities or U.S. officials about the reported defection.

Last month, Syrian troops and their Iran-backed allies circled around U.S.-backed rebels and reached the border with Iraq. The move dealt a blow to the declared U.S. mission to defeat IS in the desert region.

Abdurrahman said four others defected and joined the Islamic State group but no other activists confirmed the claim.