Syrian Foreign Minister Walid al-Moallem warned that its delegates at peace negotiations in Geneva will leave today if "serious talks" do not start.

Mr Moallem gave the deadline for talks to begin to United Nations mediator Lakhdar Brahimi after the UN said the rebel and government delegations would not meet face-to-face as originally hoped.

The Western-backed opposition, which agreed to the talks only under intense diplomatic pressure, said it was not yet willing to sit down with the government it aims to overthrow.

The main negotiations had been due to begin at the United Nations headquarters.

Syrian TV said Mr Moallem told Mr Brahimi that if "serious talks don't begin on Saturday, the official Syrian delegation will have to leave because the other party is not serious or ready."

Bouthaina Shaaban, an adviser to President Bashar al-Assad, blamed the rebel coalition and questioned whether it was prepared to negotiate an end to the violence.

"We came here with Syria and the Syrian people on our mind, while they came here with positions and posts on their mind," she said.

Rebel Syrian National Coalition opposition leader Ahmed Jarba had laid out his demands for talks, calling for the creation of a transitional government that did not include Mr Assad.

Mr Jarba insisted on ignoring the reality that the tide of the war had turned against the rebels and asserted to reporters: "We have started to look into the future without him.

"Assad and all of his regime is in the past now. This regime is dead," he claimed baldly.

But the Syrian president's officials have insisted that he is not going anywhere.

And US Secretary of State John Kerry also admitted that there was no sign that President Assad was ready to quit, although he continued to insist that the Syrian leader had no place in his country's future.

Meanwhile, Lebanese Hezbollah fighters fought alongside Assad loyalists in eastern Ghuta against rebels, including extremists from the Islamic State of Iraq and the Levant group.