Syrian government negotiators are still unsure whether they will return to continue peace talks in Geneva after they flew back to Damascus this weekend, a government source said Monday.

The government's chief negotiator Bashar al-Jaafari had told reporters in Geneva on Friday that his team would go home to Syria and that "Damascus will decide" whether they would return to the UN-backed talks.

"For the time being there has been no final decision. Damascus is still thinking about the feasibility of its participation," the government source told AFP on condition of anonymity.

"As soon as a decision is reached, it will be made public through the usual diplomatic channels."

A spokesman for the opposition delegation, Yahia al-Aridi, said meanwhile that his side's chief Nasr al-Hariri would be back in Geneva on Monday evening.

The office of UN special envoy Staffan de Mistura, who is mediating the talks, made no announcements Monday on the planned return to negotiations.

De Mistura had said the negotiations would resume Tuesday.

But after meeting with de Mistura Friday, Jaafari said there were "big problems in this round of talks," pointing to a communique published by the opposition last month in Riyadh signalling it was maintaining its insistence on Assad's removal.

The opposition, united in one delegation for the first time, has defied calls to give up on its demand that Assad must step down before any peace deal can be reached.

"The language was provocative, irresponsible politically speaking," Jaafari said, warning that if the opposition delegation stuck to such language "there will be no progress."

The government delegation had initially refused to confirm that it would attend the eighth round of UN-backed talks at all, and arrived a day late.

Syria's six-year war has claimed more than 340,000 lives, forced millions to flee their homes and left the country in ruins.