Syrian government negotiators will remain in Damascus on Tuesday and Wednesday, a source close to the delegation said, skipping the scheduled resumption of United Nations-led peace talks in Geneva.
"The delegation will not leave today or tomorrow for Geneva, and the final decision (on attending) has not been taken yet," the source told AFP on Tuesday.
An eighth round of peace talks aimed at ending Syria's nearly seven-year war began in Geneva last week.
UN Syria envoy Staffan de Mistura announced shortly after the talks began that they would be extended by two weeks.
Negotiations were paused over the weekend, but both sides were expected to return to Geneva to resume discussions scheduled to begin on Tuesday.
However, the Al-Watan newspaper, which is close to the government, said the regime's delegation was in Damascus and was not expected to leave either Tuesday or Wednesday.
The daily said the invitation to return to the talks "is still being studied by the Syrian leadership".
Meanwhile, the opposition delegation to the talks said its head Nasr al-Hariri had arrived in Geneva and would meet de Mistura on Tuesday afternoon.
On Monday, a government source had already cast doubt on the return of the delegation to the 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, speaking on condition of anonymity.
"As soon as a decision is reached, it will be made public through the usual diplomatic channels."
The government delegation left Geneva on Saturday, after its chief negotiator Bashar al-Jaafari said there were "big problems in this round of talks".
He was referring to a communique published by the opposition last month in Riyadh signalling that it was maintaining its insistence on President Bashar al-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.
Jaafari described that position as "provocative" and "irresponsible", warning that "there will be no progress" if the opposition maintained that position.
De Mistura has tried to maintain an upbeat note on the talks, and on Friday he published a document suggesting 12 principles for a future Syria that he suggested the two sides could agree, including that the country "shall be democratic and non-sectarian".
He asked the parties to discuss the points and add their thoughts before the talks resumed.
More than 340,000 people have been killed in Syria since the conflict began with anti-government protests in March 2011.