President Trump canceled the CIA’s secret program to arm and train Syrian rebels fighting the regime of Syrian strongman Bashar al-Assad — a move critics called a gift to Russia, a new report said Wednesday.

“This is a momentous decision. Putin won in Syria,” a US official who supported the program told the Washington Post.

The program to arm moderate Syrian rebels began under the Obama administration in 2013 and was continued under Trump until now.

Officials told the paper that phasing out the covert program was a way to improve relations with Russia and President Vladimir Putin, who strongly opposed the effort.

The officials said the president made the call after an Oval Office sitdown with CIA Director Mike Pompeo and national security adviser H.R. McMaster ahead of Trump’s meeting with Putin at the G20 in Germany on July 7.

The move comes three months after the US bombed a Syrian airfield in retaliation for a chemical attack launched by Assad’s forces on rebel positions.

UN Ambassador Nikki Haley said at the time that “in no way do we see peace in that area with Assad at the head of the Syrian government.”

Trump and Putin discussed a limited cease-fire in Syria at the meeting in an area where the CIA-backed rebels were doing much of the fighting.

The report came as Team Trump is under a microscope for its dealings with Russia.

Special counsel Robert Mueller is investigating Russia’s meddling in the US election and possible collusion by the Trump campaign.

Analysts said the rollback could create a vacuum that may be filled by more radical elements in the country’s brutal civil war.

“We are falling into a Russian trap,” Charles Lister, a senior fellow at the Middle East Institute, told the paper.

“We are making the moderate resistance more and more vulnerable … We are really cutting them off at the neck.”

Others said it simply reflected the reality of the situation on the ground, where Assad, backed by the Russians, appeared to be gaining the upper hand.

“It’s probably a nod to reality,” said Ilan Goldenberg, a former Obama administration official and director of the Middle East Security Program at the Center for a New American Security.