Lakhdar Brahimi, the UN-Arab League joint envoy, has called for talks between the Syrian opposition and an "acceptable delegation" from the Damascus government on a political solution to the country's 23-month-old civil war, Al Jazeera reported.
In a joint press conference in Cairo with Nabil Elaraby, the Arab League secretary-general, Brahimi said on Sunday that negotiations could begin on UN premises. He gave no specific location.
The initiative of opposition leader Mouaz al-Khatib, which calls for talks with any Syrian representative not directly involved in repression, "has opened the door and challenged the Syrian government to live up to what it has been continuously saying, that it is ready for dialogue and a peaceful solution", Brahimi said.
Khatib, the head of the Syrian National Coalition, offered last week to hold talks with President Bashar al-Assad's ceremonial deputy, Farouq al-Sharaa, on a political transition in which Assad would be given safe passage to go into exile.
"We believe that if a dialogue begins at the offices of the UN, at least at the start, between the opposition and an acceptable delegation from the Syrian government, we think this will be a start to get out of the dark tunnel," Brahimi said.
It was unclear whether he had received any indication of Syria's willingness to enter into talks with Khatib and his bloc.
Meanwhile, Elaraby said he will travel to Russia, one of Assad's main foreign allies, on Tuesday for talks with envoys of four Arab states. Syrian Foreign Minister Walid Moualem is also due to visit Moscow later this month.
Brahimi confirmed that Khatib would himself visit Moscow next month, adding that he had discussed that trip with Elaraby.
The latest diplomatic development came as rebels pressed an offensive in northern Syria, attacking Aleppo airport and two airbases.
Regime troops fended off fierce rebel onslaughts around Aleppo international airport and the adjacent Nayrab military airbase on Saturday
East of Aleppo, rebel attacks around the Kwiyres military airbase sparked counter attacks from government warplanes.
Opposition fighters launched the so-called Battle of the Airports on February 12, and they have since seized Al-Jarrah military airport and a military complex entrusted with securing Aleppo's civilian airport.
Rebels on Saturday also overran a military police checkpoint in the Golan Heights town of Khan Arnabeh just beyond the outer ceasefire line along the demilitarised zone bordering Israel, the UK-based Syrian Observatory for Human Rights said.
Regime forces responded by shelling Khan Arnabeh and the nearby village of Jubata al-Khashab, inside the ceasefire zone, forcing a rebel retreat.
The Israeli military said it had taken seven Syrians wounded in clashes on the Golan to a hospital inside the Israeli borders.
Soldiers provided medical care to the injured Syrians "adjacent to the security fence" on the strategic plateau, the army said, without giving further details about them.