BEIRUT - Just when they expected a flood of heavy weapons to help them make a major push against the forces of President Bashar Assad, rebel commanders in Syria say, arms shipments from outside the country have instead slowed, prolonging a conflict now nearing the end of its second year.
Although rebels have made gains in the north and east, seizing military bases and checkpoints, opposition figures who had made predictions of quick victory now say their arsenal is at a level that can support only a war of attrition.
"There will be no quick and practical end," said Nabil Amir, spokesman for the Damascus Military Council, a key rebel group.
Although arms for the Syrian opposition have come primarily from Arab states in the Persian Gulf region, rebel commanders almost uniformly blame the slowdown on the United States, which they suspect of exerting pressure on its regional allies.
Commanders of Syria's fractured opposition said they believed they had been promised weapons as an incentive to unite. In December, provincial councils in the Free Syrian Army, an opposition umbrella group, gathered from across the country under the banner of a Supreme Military Council at the behest of Qatar and Saudi Arabia.
"We were promised that if we unified our ranks that we would be given legitimacy as well as salaries and heavy weapons," said Col. Qassim Saad Eddine, a member of the 30-member council. "But from that day we have gotten nothing."
The reluctance of Arab and Western countries to arm the rebels is based at least in part on concern that the weapons would fall into the hands of groups that those nations view as extremist. But it has paradoxically served to increase the influence of Islamist fighters in Syria, who have emerged as the best-armed members of the insurgency.
Strong and better disciplined, the Islamists have had more success in capturing Syrian military weapons. Some people suspect they also benefit from wealthy supporters, possibly linked to al-Qaida.
Top Pentagon officials, including Defense Secretary Leon E. Panetta, recently revealed that they had supported a recommendation last summer by the State Department and CIA to arm the rebels, but were overruled by the White House.
And on Monday, the European Union decided to continue its arms embargo against both sides in the conflict.
Last year, a steady flow of predominantly light weapons, most shipped through Turkey from the gulf states, enabled rebels in northern Syria to destroy government tanks, down attack helicopters and fighter jets, and seize large swaths of Aleppo and Idlib provinces. Weapons that did not come in with the aid of Turkey _ frequently bought on the Turkish black market or in Iraq _ were smuggled across the porous border, rebels said.
In the fall, under pressure from Saudi Arabia and Qatar, Jordan allowed several shipments of light arms from the gulf to flow to opposition fighters in southern Syria, according to Lt. Col. Mohammad "Abu Saleh" Khair Harbaat, an officer with the Dara Military Council, the main rebel umbrella group in the region.
Freshly armed, some rebels were sent to Damascus, the capital, where they spent a week studying potential targets. They settled on the presidential palace, a symbolic choice that was meant to mark an escalated offensive on the city. The strike reportedly caused minor damage.
"The purpose in specifically hitting the palace was to show that we are able to hit any place and any target," said 1st Lt. Omar Hariri, who had defected from the Syrian army more than a year earlier. "It raised the spirits of the revolutionaries."
But it soon became clear that predictions of a quick victory were wildly unrealistic. Jordan has stanched the flow of small arms across its border and weapons shipments to the rebels from Turkey and gulf states have dwindled, said Mohammad Qaddah, a member of the 60-seat Syrian National Coalition and a civilian commander of the Freemen of Houran brigade in southern Syria.
"What is clear is that fewer weapons are getting in and that it has had consequences on the ground," said a Western diplomat based in Lebanon. "The regime has had two pretty good months on the ground and the rebels are on the defensive."
Opposition activists reported Tuesday that more than two dozen people, many of them children, had been killed in what may have been a surface-to-surface missile attack on an Aleppo neighborhood. There was no comment from the government.
An example of the rebels' unrealized expectations came late last year when commanders in the central province of Hama decided to capitalize on a sense of momentum. Anticipating an influx of heavy weapons from Arab and Western nations, they announced an offensive to seize control of Hama.
On the first day of the operation, rebel fighters said they had seized almost a dozen towns and villages and numerous checkpoints. Three days in, they reported downing three MIG fighter jets using a Soviet-era antiaircraft weapon.
But the fighters soon ran out of ammunition and the weapons they were expecting never arrived. Early this month, the last of the opposition-held villages fell back into government hands as rebels were forced to withdraw.
Outside support is elusive, analysts say, because donor countries worry that the unified opposition command is not really in control of all the rebel groups, and Western nations fear that weapons will fall into the hands of extremists.
In December, as the Syrian National Coalition, the umbrella political opposition group, received international recognition, the United States blacklisted the Islamist rebel group Al Nusra Front, accusing it of being an alias for the group al-Qaida in Iraq.
Al Nusra Front, which has militias across Syria, is not affiliated with the Free Syrian Army but regularly fights alongside its groups.
Qaddah said meetings with U.S. officials in Egypt, Jordan and elsewhere had been mostly fruitless.
"Every time we sit with American Army officers, they say, 'We want to help you,' and we say, 'When?'" Qaddah said.
Mohammad Ajlouni, who began the pro-opposition Syria Alshaab TV channel and has lobbied in the U.S. to arm the opposition, said the hesitation by the West and Arab states is based on a fear of an Islamist future for Syria.
"They know Assad is going to leave, but they don't want him to leave before they know who will replace him," he said. "That's why they are drying out all of the weapons to the revolution, because they are worried that [Al Nusra Front] will be victorious."
On Monday, a U.N. panel investigating human rights violations in Syria issued a report expressing concern that the conflict had "become increasingly sectarian, with the conduct of the parties becoming significantly more radicalized and militarized." It estimated that as many as 70,000 people had died in the fighting, and accused both sides _ but especially the government _ of human rights violations. The drawn-out war has apparently eroded support for the opposition without necessarily increasing support for Assad.
At a news conference last month that followed a trip to the Mideast by a group of U.S. senators, in part to meet with Syrian opposition leaders, Sen. John McCain, R-Ariz., again pushed for the U.S. to arm the rebels.
"I believe more than ever that we need to give them weapons and we need to establish a no-fly zone," he said. "It's very clear that air power is the major asset that Bashar Assad has in basically ... his ability to maintain what is clearly a stalemated situation, or certainly a very slow process."
In early January, Jordan resumed small shipments to the militias, including some heavy weapons. Photos sent by Harbaat, with the Dara Military Council, show a recoilless rifle, which can take out tanks or fortified positions, and a 40-millimeter grenade launcher, which can be used against tanks and armored vehicles.
The introduction of the heavy weapons has corresponded with gains in Dara, the birthplace of the Syrian revolution, which had mostly remained under tight government control until recently.
A few weeks after the shipments began again, they inexplicably stopped.
Special correspondent Alexandra Sandels in Stockholm contributed to this report.