Earlier this week a U.S. official said the decision was part of an effort by the Trump administration to improve relations with Russia, which along with Iranian-supported groups has largely succeeded in preserving Assad's government in the six-year-long civil war.
"It was, I think, based on an assessment on the nature of the programme, what we're trying to accomplish, the viability of it going forward," U.S. Army General Raymond Thomas, head of the Special Operations Command, told the Aspen Security Forum in Colorado.
The decision was "absolutely not a sop to the Russians," Thomas said.
Thomas, offering the first on-the-record commentary on the matter by a U.S. official, described it as a "tough, tough decision." He noted some critics thought the rebels had no chance of removing Assad from power.
The CIA programme began in 2013 as part of efforts by the administration of then-President Barack Obama to oust Assad, but produced little success.
National Security Adviser H.R. McMaster and CIA Director Mike Pompeo ended the programme after consulting with lower ranking officials and before Trump's July 7 meeting with Russian President Vladimir Putin at the G-20 summit in Germany, officials told Reuters, speaking on condition of anonymity.
It was not part of U.S.-Russian negotiations on a ceasefire in southwestern Syria, the officials said.
A downside of the CIA programme was that some armed and trained rebels defected to Islamic State and other radical groups, and some members of the previous administration favoured abandoning the programme.
Before assuming office in January, Trump suggested he could end support for Free Syrian Army groups and give priority to the fight against Islamic State.
Thomas is closely tied to a separate effort by the U.S. military to train, arm and support other Syrian fighters battling Islamic State in Syria.
U.S. special operations and other conventional forces are advising Kurdish YPG militia and other rebels fighting to retake the Syrian city of Raqqa from Islamic State. The U.S. is carrying out daily air strikes to help the advance.
Thomas said the U.S. military has come close to killing Islamic State leader Abu Bakr al-Baghdadi in recent years. In at least one case, he blamed a media leak for ruining a promising lead.
"There were points in time when we were particularly close to him," the general said.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
Get Breaking news, live coverage, and Latest News from India and around the world on NDTV.com. Catch all the Live TV action on NDTV 24x7 and NDTV India. Like us on Facebook or follow us on Twitter and Instagram for latest news and live news updates.