Despite pleas from the anti-Assad opposition, even sympathetic powers are resistant to provide arms, fearing they'll fall into the hands of Islamic extremists who have risen in the rebel ranks. At the same time, international calls for a negotiated solution have gone nowhere, mostly because both sides still seek military victory.
In this context, the report issued Monday by the U.N.-appointed Commission of Inquiry on Syria served as a grim state-of-play on the brutal conflict that the U.N. says has killed some 70,000 people since March 2011.
The 131-page report detailed deepening radicalization by both sides, who increasingly see the war in sectarian terms and rely on brutal tactics to advance their cause, spreading fear and hardship among the country's civilians.
The report accused both sides of atrocities, while saying that those committed by rebel fighters have not reached the "intensity and scale" of the government's violations.
Regime forces and its associated militias have committed crimes against humanity, the report said, citing murder, torture and rape. It said rebels have committed war crimes, including murder, torture, looting and hostage-taking.
The report also accused both sides of using child soldiers, citing the presence of fighters younger than 18 on the government side and under 15 among the rebels.
The commission said it will submit a new, confidential list of Syrians suspected of committing crimes against humanity to the U.N. high commissioner for human rights, Navi Pillay, next month.
Speaking to reporters in Geneva, commission member Carla del Ponte criticized world powers for not doing more to stop the war and called on the U.N. Security Council to refer Syria to the International Criminal Court.
"Crimes are continuing to be committed in Syria and the number of victims are increasing day to day, so justice must be done," del Ponte said.
The commission, appointed by the U.N. Human Rights Council, acknowledged that it had not been able to work inside Syria, a limitation that "significantly limited" its ability to investigate alleged abuses particularly those committed by rebels. The report covers events since July, 2012, and is based on 445 interviews with victims and witnesses.
World powers remain divided on how to handle conflict. The U.S. and many European and Arab countries have called on Assad to step down while Russia, China and Iran continue to back him.
Since Syria does not recognize the International Criminal Court's jurisdiction, it can only be referred to it by the U.N. Security Council, a move likely to be blocked by Russia and China, which have used their vetoes to shield the country before.
Also Monday, European Union foreign ministers said they were keeping an arms embargo against Syria in place for three more months, blocking a push by some to ease restrictions so some countries could arm the rebels.
An EU official said before the meeting in Brussels to decide the matter that Britain was pushing to ease the embargo. Several foreign ministers from other countries said they opposed the move.
Syria's opposition has long appealed for military aid, calling it the only way to turn the tide against Assad's forces.
But the U.S. and other countries have resisted such a move, saying there is no way to control how the arms are used and fearing they could fall into the hands of extremists.
"We are convinced that a lifting of the weapons embargo would not be reasonable," said German Foreign Minister Guido Westerwelle. "This would only lead to a new arms race in Syria. This would mean a further escalation of violence with many, many more victims."
Inside Syria on Monday, rebels overran a government checkpoint on the road the country's second-largest airport and briefly occupied a fuel station inside of it, activists said.
Rebels launched an offensive to capture the Aleppo international airport and adjacent Nairab military air base last week and have since stormed the army based charged with protecting the area.
The fall of the airport would be a turning point in the fate of the city, Syria's largest, which is now heavily damaged and divided between rebel- and government-controlled zones.
The government has not been able to fly in supplies for weeks because of the fighting.
The head of the Britian-based Syrian Observatory for Human Rights said Monday that the government has managed to bring dozens of vehicles and thousands of troops to the town of Safira, southeast of Aleppo but that heavy fighting has kept them from pushing further towards Aleppo.
Abdul-Rahman, who relies on a network of contacts inside Syria, said the army killed more than 200 members of the Jabhat al-Nusra group over the last two weeks as it pushed toward Safira. The U.S. has designated Jabhat al-Nusra a terrorist organization.
For its part, the Syrian government said its forces fought and killed "armed terrorists" in the provinces of Idlib, Homs and Aleppo. Syria blames the conflict on an international conspiracy carried out by terrorists to weaken the country.
Also Monday, the Lebanese militant group Hezbollah announced that one of its fighters had been killed while doing "his jihadist duty." It gave no further details on his death.
The announcement followed reports from Syrian activists and a Lebanese official near the Syrian border that at least two Hezbollah fighters had been killed in sectarian clashes near the Syrian town of Qusair on Saturday.
Hezbollah declined to comment on the clashes, and it could not be confirmed that the fighter buried Monday was killed in Syria.