Negotiators say they will only go to Geneva if conditions, including an end to air strikes and sieges, are met.
e Syrian opposition's High Negotiations Committee (HNC) says it is still debating whether or not its delegates will attend peace talks in Geneva, which had been scheduled to start on Friday.
The committee had set a number of conditions for its participation in the talks, including a lifting of sieges and a halt to air strikes.
"We want the talks to start, but the main obstacle is those who continue bombing our civilians and starve them," Salem al-Muslat, a HNC spokesman, told Al Jazeera from the capital of Saudi Araba, Riyadh.
The HNC later said that its negotiators would not be in Geneva on Friday because it had not received a response to its demands from the UN. It also blamed logistical problems.
The already delayed talks have been marred in controversy and disagreements over who should attend.