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 UN.’’
Saudi officials here said the United States was not barring them from providing shoulder-fired missiles but was warning about the risks. The Saudis and Qataris said they hoped to persuade 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.
US support for such weapons transfers is unlikely to materialize any time soon. President Obama’s 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.
Backing from the UN Security Council, where any intervention is blocked by the 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 UN 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. ‘‘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 region to help the rebels acquire heavier weapons.
Saudi Arabia has long had an antagonistic relationship with the government of President Bashar Assad in Syria and sees itself as the protector of Syria’s Sunni majority in a country governed by 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 a specialist on jihadi movements. ‘‘The damage from Al Qaeda was worse in Saudi Arabia than it was in the USA.’’
In May, a group of Saudi clerics 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 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 demand for greater action to defend the rebels against the Syrian government. 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.