The Syrian government on Friday warned it may quit peace talks in Geneva, accusing the opposition of being neither serious nor prepared for negotiations, state television said.
Foreign Minister Walid Muallem "has told (UN-Arab League peace envoy Lakhdar) Brahimi that should serious sessions fail to take place tomorrow, the official Syrian delegation will leave Geneva," the channel said.
Muallem told Brahimi "the Syrian delegation is serious and ready to start (negotiations), but the other side is not."
In Geneva, a source close to the regime delegation told AFP on condition of anonymity that the warning was "not a threat. It is an invitation to Brahimi to pressure the opposition into showing more seriousness."
So far, the United Nations has failed to convince the two sides to sit in the same room at the conference, which began Wednesday and is aimed at ending a three-year civil war that has claimed 130,000 lives.
On Friday morning, Brahimi met Muallem and other members of his delegation, and is set to meet with the Coalition at 4:00 pm (1500 GMT), a UN spokesman said.
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?"
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," Hakim said.
The regime rejects the opposition's contention that the Geneva I agreement requires President Bashar al-Assad to step down.
The Syrian uprising began in March 2011 with peaceful protests against the Assad family's four-decade rule, but escalated into a full-blown civil war after the regime responded with a brutal crackdown.