The U.S. and Saudi Arabia have supplied Syrian rebel groups with a small number of advanced American antitank missiles for the first time in a pilot program that could lead to larger flows of sophisticated weaponry, people briefed on the effort said.

The new willingness to arm these rebels comes after the failure of U.S.-backed peace talks in January and recent regime gains on the battlefield. It also follows a reorganization of Western-backed fighters aimed at creating a more effective military force and increasing protection for Christian and other religious minorities–something of particular importance to Washington.

This shift is seen as a test of whether the U.S. can find a trustworthy rebel partner able to keep sophisticated weapons out of the hands of extremists, Saudi and Syrian opposition figures said. The U.S. has long feared that if it does supply advanced arms, the weapons will wind up with radical groups–some tied to al Qaeda–which have set up bases in opposition-held territory.

The White House would neither confirm nor deny it had provided the TOW armor-piercing antitank systems, the first significant supply of sophisticated U.S. weapons systems to rebels. But U.S. officials did say they are working to bolster the rebels’ ability to fight the regime.

Rebels and their Saudi backers hope the Obama administration will be persuaded to ease its long-standing resistance to supplying advanced weaponry that could tip the balance in the grinding civil war–especially shoulder-fired missiles capable of bringing down planes.

Some of the TOWs provided to rebels since March are equipped with a complex, fingerprint-keyed security device that controls who can fire it, said Mustafa Alani, a senior security analyst at the Geneva-based Gulf Research Center who is regularly briefed by Saudi officials on security matters.

“The U.S. is committed to building the capacity of the moderate opposition, including through the provision of assistance to vetted members of the moderate armed opposition,” White House National Security Council spokeswoman Bernadette Meehan said. “As we have consistently said, we are not going to detail every single type of our assistance.”

Saudi Arabia and other Gulf states lobbied aggressively for the Obama administration to step up its support for the moderate opposition, especially since the collapse of the peace talks.

U.S. refusal to better arm the rebels has created strains with Saudi allies that President Barack Obama tried to mend on his recent visit to the kingdom. After the visit, senior administration officials said the two countries were collaborating more closely on material support for the rebels and the Central Intelligence Agency was looking at ways to expand its limited arming and training program based in Jordan.

A newly created moderate rebel group called Harakat Hazm said it had received about a dozen BGM-71 TOWs and was being trained on them by an unspecified allied country. It is the only group known to have received the weapons so far, though there may be others.

“To make it clear, our allies are only delivering these missiles to trusted groups that are moderate,” said one senior leader of Harakat Hazm. “The first step is showing that we can effectively use the TOWs, and hopefully the second one will be using antiaircraft missiles.”

Another Syrian opposition figure in the region confirmed the U.S., with Saudi assistance, supplied the TOW missiles.

Mr. Alani said the two countries oversaw the delivery through neighboring Jordan and Turkey to vetted rebels inside Syria. Rebels already had some types of recoilless rifles in their stocks, which can also be used against tanks and other targets. But U.S.-made TOWs are more reliable and accurate, opposition officials and experts say.

A senior Syrian opposition official in Washington who works closely with the Americans said the TOWs were part of a small, tailored program coordinated by U.S. and Saudi intelligence services to “test the waters” for a potentially larger arming effort down the road.

The official said the introduction of a small number of TOWs will have limited impact on the battlefield.

The main objective is to develop a relationship between vetted fighters and U.S. trainers that will give the Obama administration the confidence to increase supplies of sophisticated weaponry.

The U.S. has blocked Saudi Arabia from giving rebels Chinese-made man-portable air defense systems, known as Manpads.

Earlier this year, Saudi Arabia offered to give the opposition Manpads for the first time. But the weapons are still stored in warehouses in Jordan and Turkey because of U.S. opposition, according to Saudis and Syrian opposition figures.

“Basically, this is supposed to be the next step” in the eyes of rebels and their Saudi backers, Mr. Alani said of the hoped-for antiaircraft artillery.

Senior administration officials said the White House remains opposed to providing rebels with Manpads. Antiaircraft and antitank weapons could help the rebels chip away at the regime’s two big advantages on the battlefield–air power and heavy armor. The regime has used its air force to devastating effect in the civil war–frequently dropping crude barrel-bombs packed with explosives on opposition neighborhoods and cities.

In hopes of reinvigorating Western support, more moderate rebels began this year openly battling increasingly powerful extremist groups in their midst and reorganized their ranks in hopes of forming more effective fighting forces.

Harakat Hazm was created in January out of the merger of smaller secular-leaning rebel groups in the north, the main opposition stronghold. It was set up to assuage U.S. concerns that the Western-backed and secular-leaning Free Syrian Army was too fractured to be effective and that rebels weren’t doing enough to protect religious minorities.

The group is working closely with the Syrian Revolutionaries Front, another large formation of several rebel brigades that turned their guns on the extremist group Islamic State of Iraq and al-Sham (ISIS) in January. The Front was created in January to address U.S. criticism that rebels were too fragmented and that they were turning a blind eye to extremist groups. “The agreement is that the Syrian Revolutionaries and Hazm work together to get support from the international community but not step on each other,” said a member of the political opposition based in Turkey.

The official added that Hazm started to receive lethal and nonlethal aid from Saudi and the U.S. in March “because [rebels] are organizing like a proper army.”

The Western- and Gulf-backed Free Syrian Army has shaken up its ranks and strategy to try to reverse the regime’s consistent battlefield gains since last year.

“The U.S. wants pragmatic groups within the Free Syrian Army that can deal with a post-Assad Syria and secure Alawites and Christians,” said a member of the political opposition with ties to Harakat Hazm.

Syria’s conflict has strong sectarian undertones. President Assad is a member of the Alawite sect, an offshoot of Shiite Islam, and his regime is dominated by the minority group while the opposition is made up largely of Syria’s Sunni majority. Many Christians have remained loyal to the regime, hoping it will protect them.

The fate of religious minorities has been a major concern of the U.S. Several extremist rebel groups were involved in massacres of Alawite villagers last year, and desecration of Christian and Alawite religious sites, according to human rights groups.

The opposition made a point of trying to secure the Christian village of Kassab in northern Syria this month after it was overrun by extremist groups, prompting a mass exodus of its population.

Opposition leader Ahmad Jarba visited the village earlier this month and vowed that the FSA wasn’t fighting a sectarian war.

Rudayna El-Baalbaky and Mohammed Nour Alakraa contributed to this article.

April 18, 2014, 7:18 p.m. ET
By Ellen Knickmeyer, Maria Abi-Habib and Adam Entous

Find this story at 18 April 2014

Copyright ©2014 Dow Jones & Company, Inc.