Syria's divided opposition on Friday called on the regime of President Bashar al-Assad to bluntly state whether it was interested in peace talks and on what terms rather than use ally Moscow as its mouthpiece.
Louay Safi, spokesman for the Western-backed National Coalition, the main opposition group, issued the call after Russia said Damascus had agreed "in principle" to attend a peace conference in Geneva.
"We would like to hear that statement from the Assad government," said Safi, whose group is meeting in Istanbul to determine whether to attend the conference.
"This has been related to us through the Russians, I have no idea why the Syrians are silent."
The peace conference, which according to some media reports has tentatively been scheduled for June 10, is aimed at putting an end to more than two years of bloodshed in Syria that has left more than 90,000 people dead.
The conference was jointly proposed by Russia, a key backer Assad, and the United States, which supports the rebels fighting to overthrow his regime.
Russian foreign ministry spokesman Alexander Lukashevich said Russia had received the Damascus government's agreement to take part in the Geneva conference during a visit to Moscow by Syria's Deputy Foreign Minister Faisal Muqdad.
"We note with satisfaction that we have received an agreement in principle from Damascus to attend the international conference in the interest of the Syrians themselves finding a political path to resolve the conflict," Lukashevich told reporters.
Russia is seen as the nation exercising the strongest influence over the Syrian regime thanks to years of military and other cooperation that stretches back to Soviet times.
Moscow has in recent weeks also been keen to show its diplomatic influence in the region by ensuring that Assad's representatives attended a conference agreed this month by Russian Foreign Minister Sergei Lavrov and his US counterpart John Kerry.
But Lukashevich said reports of a date having been set for the conference in Geneva were premature and "cannot be taken seriously".
"Demands to immediately name a specific date for the conference without having clarity about who -- and with what authority -- will speak in the name of the opposition, cannot be taken seriously," Lukashevich said.
The Syrian opposition and its backers, including the United States, has insisted that any transition talks must lead to Assad's ouster. The Syrian leader, however, has said he won't leave before elections are held in his country.
"We would like to have guarantees particularly from the Russian side, because the Russian leadership has been defending Assad himself," said Safi.
Khaled Khoja, another member of the Coalition, said that in offering "in principle" to attend the Geneva conference, Damascus was clearly "playing with words" and trying to buy time.
He added that unless the rebels fighting the Assad regime gained the upper hand on the battle front, no political solution was in sight.
"We want the Friends of Syria (who back the uprising)... to increase their military assistance to the (rebel Free Syrian Army's) command, until Assad complies to the idea of a real political solution," Khoja said.
In addition to discussing the proposed peace conference, the three-day opposition meeting in Istanbul, which began Thursday, is aimed at resolving internal divisions and electing a new leadership.
The opposition has been under increased international pressure to present a united front and resolve internal divisions that have weakened it.