Lakhdar Brahimi, the mediator brokering the negotiations, acknowledged that the agreement on the city of Homs fell short of his hope to send a humanitarian aid convoy. He said that "to bring Syria out of the ditch in which it has fallen will take time".
Homs, one of the first cities to rise against President Bashar al Assad, once more came under mortar attacks from the Government.
Syrian Deputy Foreign Minister Faysal Mekdad said: "I assure you that 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," he told a news conference after the talks in Geneva with the Syrian opposition.
"We are ready to allow any humanitarian aid to enter into the city through the agreements and arrangements made with the UN.".
Mr Brahimi defended the pace of the talks, which have yet to touch upon the issue of Mr Assad's future.
"I think being too slow is a better way than going too fast," he said. "If you run, you may gain one hour and lose one week."
Mr Brahimi said the thorniest topic - a possible transitional government - will not come up until at least tomorrow.
"I think this belittles the importance of this conference and the goal that was drawn for it," said Bouthaina Shaaban, an adviser to Mr Assad.
The Western-backed opposition, made up largely of exiled Syrians, says Mr Assad has lost legitimacy and can no longer lead a country after unleashing the military on largely peaceful protests nearly three years ago.
The Government says the rebellion is rife with terrorists and that Assad is the only person able to end the fighting that has killed more than 130,000 people.
In the meantime, the homegrown rebellion has become a regional proxy war between Iran and Saudi Arabia, with foreign fighters flooding in on both sides.
Homs was considered a promising place to start the negotiations. The city was one of the first areas that plunged into armed conflict in 2011. Neighbourhoods in the old city have been ravaged following repeated government assaults to reclaim control from rebels.
The city had a pre-war population of one million, but most residents have since fled. Activists say 800 families are trapped, without regular access to food, medicine and basic necessities.
A senior US official said: "The situation in Homs is extremely urgent. Anything the Government says to the contrary is false."
Monzer Akbik, an opposition spokesman, said the coalition was still determined to stay for the political talks set to begin tomorrow. He accused the Government of using "stalling techniques".
Syrian activists, including the Britain-based Syrian Observatory for Human Rights, said some rebel-held districts in Homs came under attack this morning by mortars fired by Syrian Government forces.
Heavy fighting continued yesterday in the Qadam neighbourhood on the southern fringe of Damascus, where at least 35 rebels and government troops were killed the previous day.