Russia would eventually support an international war crimes tribunal for Syria, Russia's foreign minister has said.
Russia has been one of the Syria's closest allies since the conflict began more than two years ago.
"At this stage, I think the first priority is to end the violence as soon as possible to avoid more civilian deaths," Sergey Lavrov, the Russian foreign minister, said on Friday.
"And these calls for not allowing impunity are totally correct, but what I notice is that certain people try to use that to slow down discussions and have the reconciliation process cancelled, which will only lead to more deaths."
Meanwhile, a team of UN experts are waiting for approval to enter Syria to investigate alleged chemical weapon attacks.
A team of UN-led experts is on standby in Cyprus waiting for the go-ahead to probe allegations of chemical weapons attacks in Syria, but the mission has been held up by diplomatic wrangling over their powers and how to keep them safe.
The team of at least 15 investigators includes analytical chemists, able to collect and test suspected samples, and World Health Organisation experts on the medical effects of exposure to toxins, who could examine alleged victims.
Supply lines threatened
Syrian soldiers backed by warplanes battled rebels for control of strategic hilltop villages near the Lebanese border on Friday, as government troops step up counterattacks against opposition forces threatening regime supply lines on the country's frontiers.
Bomb blasts and shots fired into the air to mourn a fallen Syrian government soldier could be heard on the Lebanese side of the border as fighting raged around Qusair, a contested central Syrian town near a key highway between Damascus and the coast.
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The battles there came as government forces launched a second offensive against rebels in the province of Daraa on the Jordanian border, where the opposition has been making steady advances in recent weeks.
While Syrian president Bashar al-Assad's forces are stretched thin and much of the country has been allowed to slip into the hands of the rebels, the government is still fighting hard to keep control of airports, seaports, and roads linking them to the capital Damascus that are seen as essential to its survival.
Also on Friday, activists said rebels clashed with troops in the northeastern border city of Qamishli, two kilometers away from the border with Turkey.
Fighting is rare in the predominantly Kurdish and Christian city, where rebels usually maintain a truce with the government.
It was not clear what prompted the clashes, which according to the Britain-based Syrian Observatory for Human Rights included members of Jabhat al-Nusra, an Islamist group that recently announced a merger with the Iraqi branch of al-Qaeda.
Syria's rebels have gained momentum and made significant gains in the past weeks, largely due to an influx of arms. Arab officials and Western military experts say Mideast powers opposed to Assad have stepped up weapons supplies to Syrian rebels, with Jordan opening up as a new route.