The UN-Arab League special envoy charged with brokering peace in Syria, Lakhdar Brahimi, said on Wednesday that he hoped Russia and the US would exert influence over the main parties in Syria's war to bridge "quite large" gaps that remained.

Brahimi also said that the United Nations and Syria's government continued to negotiate access for aid to the rebel-held Old City of Homs. The UN mediator added that the Syrian government and main opposition group were unlikely to make major progress before the end of the current round of talks on Friday.

"To be blunt, I do not expect that we will achieve anything substantive," Brahimi said at a news conference in Geneva on Wednesday after meeting the government and opposition for preliminary talks on a transitional governing body first proposed in a 2012 roadmap. "I am very happy that we are still talking, but the ice is breaking slowly, but it is breaking."

The original Geneva roadmap was written during the first talks, in June 2012, seeking a peaceful political solution to the civil war in Syria. It was agreed to by both the United States and Russia, which, respectively, back the opposition and the regime of President Bashar al-Assad. The current talks had been deadlocked for days as the opposition sought negotiations on a transitional government - claiming for the first time on Wednesday that this process had begun.

"For the first time, now, we are talking about the transitional governing body," Louay Safi, the opposition delegation's spokesperson, said earlier on Wednesday. "We will talk about the details in the coming days: the size of the body, its duties, the length of its mandate," Safi added.

Talks continue on humanitarian issues, which include aid for an estimated 3,000 civilians in the central city of Homs. Brahimi has portrayed relief plans for people there and in other besieged areas and the release of detainees held by both sides as confidence-building measures that could help the warring factions bridge their larger differences on political issues.

mkg/msh (Reuters, AFP, dpa, AP)