DAMASCUS (AFP) - Syria is threatening to quit peace talks in Geneva by Saturday, criticising the opposition delegation as "not serious," state television said.

Foreign Minister Walid "Muallem has told (UN-Arab League peace envoy Lakhdar) Brahimi that should serious sessions fail to take place by tomorrow, the official Syrian delegation will leave Geneva," the channel said on Friday.

The regime accused the opposition National Coalition of being "not serious and not ready" for the talks, which opened on Wednesday.

Despite attempts on Thursday, the United Nations has so far failed to convince delegations representing the two warring sides to sit in the same room.

Syrian Deputy Foreign Minister Faisal Muqdad told reporters the opposition was obstructing the talks.

"The problem is that these people do not want to make peace; they are coming here with pre-conditions," he told reporters.

"Of course we are ready to sit in the same room. Why are we coming here then," he asked.

Mr Nazir al-Hakim, a member of the opposition delegation, told AFP it was only willing to negotiate on the basis of the agreement reached at the Geneva I conference in 2012, which called for the creation of a transitional government.

"We agree to negotiate on the application of Geneva I. The regime does not accept that," he said.

"We will be in the same room when there is a clear agenda for negotiations. We need guarantees that Geneva I will be discussed," Mr Hakim said.

The regime rejects the opposition's contention that the Geneva I agreement requires Assad to go.