The US helped the RCA, a militia based out of a US military base in southern Syria, coordinate with the al-Qaeda-linked HTS

The US had foreknowledge of the offensive led by the al-Qaeda-linked Hayat Tahrir al-Sham that ousted former Syrian President Bashar al-Assad and helped another rebel group join the fight, The Telegraph reported on Wednesday.

The report said the US notified the Revolutionary Commando Army (RCA), a US-funded militia based out of a US base at Al Tanf in southern Syria, to "be ready" for an attack that could lead to the end of Assad's rule.

"They did not tell us how it would happen," Bashar al-Mashadani, an RCA commander, told The Telegraph. "We were just told: 'Everything is about to change. This is your moment. Either Assad will fall, or you will fall.' But they did not say when or where, they just told us to be ready."

In October, the US brought several other Sunni Muslim militias under the command of the RCA, swelling the force from 800 fighters to about 3,000. All of the fighters are armed by the US, and the US pays their salaries of $400 per month. The US also backs the Kurdish-led SDF in eastern Syria, but the RCA is a separate force.

When the HTS-led force began its offensive from Syria's northwest Idlib province and advanced south toward Damascus, the RCA headed north. According to The Telegraph, the US-funded group now controls about one-fifth of Syria's territory. Mashadani spoke to the paper from a former Syrian government air base that was used by Russia outside of the city of Palmyra.

Mashadani said RCA and HTS were cooperating during the offensive and that the US coordinated the communication between the two groups from Al Tanf. The US has celebrated the overthrow of Assad and made clear it's willing to work with HTS despite the fact that the group is an offshoot of al-Qaeda and designated by the State Department as a foreign terrorist organization.