The Syrian government came under pressure on Monday to allow aid trucks into the besieged rebel city of Homs as negotiators sought to keep peace talks on track by focusing on humanitarian gestures.

The government said women and children could leave Homs and government and opposition delegates also spoke of releasing prisoners.

The UN mediator said he hoped talks, which continue on Monday in Geneva, could move on to broaching the central issue that divides the two sides after three years of civil war - Syria's political future and that of President Bashar al-Assad.

Homs, occupying a strategic location in the centre of the country, has been a key battleground. Assad's forces retook many of the surrounding areas last year, leaving rebels under siege in the city centre, along with thousands of civilians.

Syrian Deputy Foreign Minister Faisal Mekdad told a news conference on Sunday that the government would let women and children leave the city centre if rebels gave them safe passage.

UN mediator Lakhdar Brahimi said he understood that they would be free to quit Homs immediately.

Mekdad said: "If the armed terrorists in Homs allow women and children to leave the old city of Homs, we will allow them every access. Not only that, we will provide them with shelter, medicines and all that is needed.

"We are ready to allow any humanitarian aid to enter into the city through the ... arrangements made with the U.N."

Western diplomats said the Syrian government should move quickly to allow this to happen or face a possible United Nations Security Council resolution, with Russia and China being urged to reverse their opposition to such a move.

"The ball is still in the regime's court. We understand that a report has gone back to Damascus seeking instructions," one diplomat said.

In Homs itself, however, opposition activists said rebels demanded a complete end to the blockade, not just a limited ceasefire. An online video showed demonstrators with Islamist flags denouncing the Geneva talks as "treachery".

Brahimi, who presided on Saturday over the first direct meeting between the two delegations, was expected to hold a another joint session on Monday to begin discussion of a UN plan for a transitional government.

Acknowledging the slow start to proceedings which began with a formal international conference on Wednesday, Brahimi said: "This is a political negotiation ... Our negotiation is not the main place where humanitarian issues are discussed.

"But I think we all felt ... that you cannot start a negotiation about Syria without having some discussion about the very, very bad humanitarian situation that exists."

There was little sign of a softening of positions on the core issue - whether or not Assad should quit now, as the opposition and their Western and Arab backers say was agreed by a U.N. conference at Geneva 18 months ago.

"The president of the Syrian Arab Republic stays until the Syrian people says something else," said Mekdad, repeating the government position that Assad can stay and win an election.

For the opposition, spokesman Louay Safi said Monday's session with Brahimi would show if the government was willing to negotiate: "Tomorrow we start talking about transition from dictatorship to democracy. The regime is ... stalling."

Brahimi said opposition delegates, who have asked for the release of nearly 50,000 detainees, had agreed to a government request to try to provide a list of those held by armed rebel groups - though many of these groups, fighting among themselves, do not recognize the negotiators' authority.

Mekdad said the government had examined an opposition list of 47,000 people believed to have been arrested by Assad's forces and found most had either never been held or were now free. He also denied that any children were being held.

Russian Foreign Minister Sergei Lavrov, whose government has helped Assad resist Western pressure but backs a negotiated peace to prevent the conflict spreading, called for progress on aid, unblocking besieged areas and prisoner exchanges.

Underlining the difficulty of implementing even local agreements on the ground, a U.N. agency trying to deliver aid to a besieged rebel area of Damascus said state checkpoints had hampered its work, despite assurances from the government that it would allow the distributions.

Profound mutual mistrust and the absence from Geneva of powerful Islamist opposition groups make any substantial progress very difficult, and previous aid deals and ceasefires in Syria have proved short-lived.-Reuters