BEIRUT/AMMAN (Reuters) - Syrian rebels said on Thursday a U.S. decision to halt a covert CIA program of military aid would mark a big blow to the Syrian opposition and risked allowing jihadists to tighten their grip over the insurgency.

FILE PHOTO: A rebel fighter walks past damaged buildings in a rebel-held part of the southern city of Deraa, Syria June 22, 2017. REUTERS/Alaa Al-Faqir/File Photo

Rebels who have received aid under the CIA program said they had yet to be informed of the U.S. decision first reported by the Washington Post on Wednesday and confirmed by two U.S. officials to Reuters.

A Free Syrian Army (FSA) commander said the U.S. decision risked triggering the collapse of the moderate opposition, which would benefit President Bashar al-Assad and jihadists linked to al Qaeda that have long sought to extinguish more moderate groups.

Other rebel sources said much would depend on whether U.S.-allied regional states Jordan, Saudi Arabia, Qatar and Turkey kept up their support to groups fighting under the FSA banner, which had been the focus of the CIA program.

“We heard nothing about this,” said an opposition official familiar with the program, describing the decision as a complete surprise.

The U.S. decision compounds an already bleak outlook for the Syrian opposition that has been battling since 2011 to unseat Assad, who appears militarily unassailable thanks in large part to staunch Russian and Iranian backing.

The CIA program which began in 2013 funneled weapons, training and cash to vetted FSA groups via Jordan and Turkey.

It regulated aid to the rebels after a period of unchecked support early in the war - especially from Gulf states - helped give rise to an array of insurgent groups, many of them strongly Islamist in ideology.

The support in some cases included anti-tank missiles that helped the rebels make big advances against the depleted Syrian army, triggering Russia’s intervention in September 2015.

FSA rebels have long complained the support fell well short of what they needed to make a decisive difference in the war against the better armed Syrian army and the Iran-backed militias helping it, including Lebanon’s Hezbollah.

One of the U.S. officials said the decision was part of a Trump administration effort to improve relations with Russia.

Critics of the CIA program, including some U.S. officials, have also said some of the armed and trained rebels defected to Islamic State and other radical groups.

Kremlin spokesman Dmitry Peskov declined to comment when asked what he thought about the U.S. move and said only that U.S. President Donald Trump and Putin did not discuss the issue when they met at a G20 summit earlier this month.

“We welcome all the efforts aiming at de-escalation of the situation and building security in the Middle East. It’s OK if that is what it’s all about,” deputy foreign ministry spokesman Artem Kozhin told a news briefing on Thursday, according to Interfax.

NOT IN OUR INTEREST

Before taking office in January, Trump suggested he could end support for FSA groups and give priority to the fight against Islamic State.

A separate U.S. military effort to train, arm and support other Syrian rebels with airstrikes and other actions will continue, the U.S. officials said. The U.S. military support has included backing for Kurdish fighters battling Islamic State.

Groups included in the CIA program operate mostly in northwestern and southern Syria.

“Certainly this decision will have results and consequences on the Syrian scene, particularly in the north and the south. The halt of support to the FSA by the international community is a factor in escalation of Assad’s strength and the strength of the extremist groups,” the FSA commander said.

Backed by Jordan, FSA groups in southern Syria have helped contain jihadists such as the group formerly known as the Nusra Front, and have gone on the offensive against Islamic State.

FSA groups in northern Syria have had a tougher time withstanding the jihadists. Aid to the FSA in the northwest was temporarily suspended earlier this year following a major jihadist assault against them.

“The Americans have been informing us they have reached serious agreements with the Russians. The Americans are saying they have a new strategy toward Syria which is not like that of the Obama era,” said another rebel commander.

“Is this in our interest? Of course not,” the commander said of the reported U.S. decision. “We are waiting to see.”

Turkey has supported FSA groups outside the CIA-backed channels to advance its interests in northern Syria, notably in its Euphrates Shield campaign last year that carved out a de facto buffer zone at the frontier.