The plan to train and equip rebels opposed to Mr Assad was started in 2013 under the administration of Barack Obama, as an effort to try and put pressure on the Syrian leader to step aside. While most of the heavy weapons and cash were provided by Saudi Arabia, the CIA took the lead in the training.
Now, it has been reported that Mr Trump has decided to cancel the programme, something that will likely be welcomed by Russia, which has for years supported the Assad regime.
The limited CIA programme – known as Timber Sycamore – also received funding from Qatar, Jordan and Turkey. It was seen by the Obama administration as a limited means of offering support in a conflict in which it had no interest in placing US troops on the ground.
A second programme, overseen by the Pentagon, was aimed at training rebels to combat Isis fighters in Syria. The programme was halted last year after it emerged that despite spending more than $500m, with the aim of training up to 5,000 rebels, it resulted in just five trained fighters.
The Washington Post said that the decision to scrap the CIA programme was made a month ago, after a meeting with CIA Director Mike Pompeo and national security adviser HR McMaster, and before the July 7 meeting in Germany with Russian President Vladimir Putin at the G20.
After the meeting between the two leaders, the US and Russia announced a new cease-fire in southwest Syria, along the Jordanian border, where many of the CIA-backed rebels have reportedly long operated.
John Pike, Director of the military and strategic research group GlobalSecurity.Org said the CIA programme was one of the biggest funding of foreign militia in its history. The Pentagon programme, by contrast, had been a huge failure.
“I think Putin will be thrilled,” he told The Independent. “Now America has the option of backing [Isis] or backing Assad.”