The United Nations on Tuesday sent out invitations to new Syria peace talks in Geneva this week, as leading opposition representatives debated whether to attend.
UN Syria envoy Staffan de Mistura's office said it had issued invitations to the talks, which are scheduled to begin on Friday, but without saying who had been invited.
The talks have already been delayed from their scheduled start on Monday over who will represent the opposition.
The High Negotiations Committee (HNC), a body representing key opposition groups and factions, insists it should be the sole opposition delegation.
But several opposition figures who do not belong to the body told AFP on Tuesday they had been invited to the talks.
The HNC met in Riyadh to debate whether it would attend, with a source close to the meeting confirming the body had received invitations to Geneva, but discussion on whether to participate was ongoing.
"The response will be a request for clarifications and not an acceptance or rejection," he told AFP, adding that the body wanted to know who else had been invited and under what terms, as well as what would be discussed.
HNC member Salem al-Meslet said the group would resume talks on Wednesday, adding that the "climate is positive".
The HNC will also "ask tomorrow for clarifications (from the UN) concerning some issues, particularly humanitarian issues", he said.
A statement from the HNC said it insisted on "the need for an improvement on the ground to pave the way for the negotiating process", including lifting sieges and aid deliveries.
Several opposition figures who are not part of the HNC said they have been invited, according to AFP.
"I am on my way to Geneva after receiving an invitation," said Qadri Jamil, a former deputy Syrian premier who was sacked in 2013 and has good ties with Russia, a longtime ally of Syrian President Bashar Al-Assad.
And Haytham Manna, a longstanding opposition figure who is co-chair of the political wing of a Kurdish-Arab alliance, also said he had been invited.
"I received an invitation to participate in the talks as a negotiator," he told AFP.
Syria's most powerful Kurdish party, the Democratic Union Party (PYD), said it had not yet received an invitation.
The PYD is not part of the HNC, and leading opposition backer Turkey has said it will boycott the talks if it is invited, noted AFP.
The talks in Geneva are the latest international attempt to end Syria's conflict, which has killed more than 260,000 people since it began with anti-government protests in March 2011.
They are part of a UN-backed plan agreed last year that envisages negotiations, followed by the creation of a transitional government, a new constitution, and elections within 18 months.
Delegations are expected to engage in "proximity talks", rather than face-to-face discussions, which will run over six months.
The first round is expected to last between two and three weeks.
Syria's regime has designated its UN envoy Bashar al-Jaafari as its chief negotiator, with its deputy foreign minister heading its delegation.
De Mistura’s previous efforts to stop fighting in Syria have been unsuccessful. He previously angered rebel groups by saying Assad was "part of the solution" to the conflict in Syria. Those rebel groups later refused to a temporary ceasefire because of de Mistura’s comments.
AFP contributed to this report.