RIYADH, Saudi Arabia -- For months, Saudi Arabia and Qatar have been funneling money and small arms to Syria's rebels but have refused to provide heavier weapons, like shoulder-fired missiles, that could allow opposition fighters to bring down government aircraft, take out armored vehicles and turn the war's tide.
While they have publicly called for arming the rebels, they have held back, officials in both countries said, in part because they have been discouraged by the United States, which fears the heavier weapons could end up in the hands of terrorists.
As a result, the rebels have just enough weapons to maintain a stalemate, the war grinds on and more jihadist militants join the fray every month.
"You can give the rebels AKs, but you can't stop the Syrian regime's military with AKs," said Khalid al-Attiyah, a state minister for foreign affairs in Qatar. Providing the rebels with heavier weapons "has to happen," he added. "But first we need the backing of the United States, and preferably the U.N."
Saudi officials here said the United States was not barring them from providing shoulder-fired missiles, but warning about the risks. The Saudis and Qataris said they hoped to convince their allies that those risks could be overcome. "We are looking at ways to put in place practices to prevent this type of weapon from falling into the wrong hands," one Arab official said, speaking on the condition of anonymity in line with diplomatic protocol.
American support for such weapons transfers is unlikely to materialize any time soon. The Obama administration has made clear that it has no desire to deepen its efforts, mostly providing logistical support for the rebels.
Administration officials would not comment on what they are telling their Persian Gulf allies about arming the rebels. "We are doing what we feel is appropriate to help the unarmed opposition to be more effective and working closely with the opposition to prepare for a transition," the State Department said in response to a question on the subject.
Backing from the United Nations Security Council, where any intervention is blocked by the firm vetoes of Russia and China, seems even less likely. Nor is the call for an Arab-led military action in Syria, voiced two weeks ago by the emir of Qatar at the United Nations General Assembly, expected to bear fruit.
Many Saudi and Qatari officials now fear that the fighting in Syria is awakening deep sectarian animosities and, barring such intervention, could turn into an uncontrollable popular jihad with consequences far more threatening to Arab governments than the Afghan war of the 1980s.
"If the killing continues, the youth will not listen to wise voices," said Salman al-Awda, one of this country's most prominent clerics, in an interview at his office here. "They will find someone who will encourage them, and they will go."
Already, there are signs of an uptick in the number of young men crossing illegally into Syria from Saudi Arabia and other Muslim countries, and of private fund-raising efforts across the gulf to help the rebels acquire heavier weapons. The fighting has also spilled into Turkey, which shelled Syria for four days last week after a Syrian shell killed five Turkish civilians.
Saudi Arabia has long had an antagonistic relationship with the government of President Bashar al-Assad in Syria, and sees itself as the protector of Syria's Sunni majority in a country governed by Mr. Assad's Alawite minority. But the prospect of an increasingly sectarian civil war in Syria is deeply troubling to many here, where the Afghan jihad spawned a generation of battle-tested zealots who returned home and waged a bloody insurgency that was brought under control only recently.
"The government really doesn't want to repeat the experience we had with the guys who went to Afghanistan and Iraq," said Mshari al-Zaydi, a Saudi columnist and an expert on jihadi movements. "The damage from Al Qaeda was worse in Saudi Arabia than it was in the U.S.A."
In May, a group of conservative Saudi clerics, including some who had called for volunteers to fight in Iraq, announced a fund-raising drive on Facebook to support the Syrian rebels. Days later, they posted messages saying the government had barred them from sending donations.
Some clerics criticized the government's restriction, including Mr. Awda, who sent an apparent warning on Twitter: "The donations to Syria cannot be limited to this route or that route, and those who want to provide support will find a way."
The Saudi government must also manage the rising popular demand for greater action to defend the rebels against the Syrian government, widely seen here as a proxy for Saudi Arabia's arch-nemesis, Iran. Behind these political fault lines lies a deep sectarian hostility: Saudis are increasingly angry about the mistreatment of their fellow Sunni Muslims in Syria by an Alawite regime they see as heretical.
"There is deep anger," said Abdelaziz al-Gasim, a prominent lawyer in Riyadh with a reformist reputation. "People want the government to do more." The calls for greater involvement are a rare point of accord between Saudi liberals and conservatives, he added, though they are more visible on the free zone of Twitter than in traditional media.
Already, regional Islamist funding networks are being built up, Mr. Gasim said. "These are private channels with people in Kuwait and Qatar, and you cannot control them -- there are deep business relationships in the gulf," he said. "And the majority of them are within the Islamic movement, because the more nationalist or secular movements in Syria have no relationship with Saudi society."
To some extent, the Saudi and Qatari governments have themselves to blame, because the major pan-Arab satellite TV stations they control -- Al Arabia and Al Jazeera, respectively -- have done more than any other outlets to stoke anger against Syria's government and urge sympathy with the rebels. Both stations have been accused of being little more than rebel mouthpieces, and they have played on sectarian fears and hatreds. In one recent and much-repeated teaser on Al Arabia for a news segment about Syria, a man with an anguished face clutches a wounded child and shouts into the camera: "Our children are dying because of Iranian fatwas!"
The Saudi government has not officially acknowledged providing arms to the rebels, and the public face of its aid has been charitable support, including a much publicized donation campaign for Syrian refugees during the holy month of Ramadan in July and August. The government is also paying the salaries of many defected Syrian officers, and financing medical assistance to Syrian refugees.
But at the Turkish border town of Antakya late last month, Syrian rebels spoke openly of the Saudi and Qatari intermediaries who dole out weapons on behalf of their governments. The chief Saudi supplier is said to be a Lebanese figure named Okab Saqr, who belongs to the political coalition of Saudi Arabia's chief ally in Lebanon, Saad Hariri.
"The amounts are not that much," said Maysara, 40, a lean rebel commander from the northern town of Saraqib, who withheld his last name for safety reasons. "They deliver weapons once every few weeks." In one recent shipment, he said, a 200-man fighting brigade received six Russian-made AS Val assault rifles, and thousands of rounds of ammunition.
Maysara added that Mr. Saqr seemed to struggle with supply issues; he once saw Mr. Saqr asking rebels for the name and contacts of a weapons dealer from the former Yugoslavia that he was hoping to meet. The logistics of acquiring and distributing weapons in such a chaotic environment are daunting, and the rebels are anxious about infiltration by the Syrian government's notorious intelligence agents.
The Saudi government appears to be trying to finance more secular rebel groups, Maysara said, while the Qataris appear to be closer to the Muslim Brotherhood. But these distinctions are slippery, in part because rebel groups adapt their identities to gain money and weapons. One group, in an almost comical bid for support, named itself the Rafik Hariri brigade, after the former Lebanese prime minister and Saudi ally who is believed to have been assassinated by the Syrians, and whose son Saad is influential in doling out Saudi support to the rebels.
Mr. Awda, the Saudi cleric, said reports of the chaotic situation at the Turkey-Syria border had become a staple of popular complaint in Saudi Arabia.
"People are repeating rumors that people inside Syria receive almost nothing of what is being given," he said, "and that those who are arranging it do not have the experience to deal with this." Those reports, he added, augment the desire of many Saudis to take matters into their own hands and set up new channels to the rebels.
Michael R. Gordon contributed reporting from Washington.
This article originally appeared in The New York Times.