Syria's armed opposition factions said in a statement on Wednesday they could not accept an invitation to peace talks which did not lead to a "transition of power to a transitional governing body".
The statement also said no steps could be taken towards a political solution to the Syrian civil war without a fully enforced ceasefire.
It said no outsiders could choose who represented the Syrian opposition at negotiations, a comment directed at UN Syria envoy Staffan de Mistura.
De Mistura had suggested on Tuesday that he could pick opposition representatives to UN-led talks in Geneva if they failed to do so.
The talks were set for 8 February but then postponed until 20 February to give the opposition more time to present a united delegation.
De Mistura warned that delays beyond the original date would force him to "select the delegation in order to make sure that it can be as inclusive as possible".
The opposition rejected the comments as "unacceptable".
"Selecting the Syrian opposition delegation is not the business... of de Mistura," wrote Riad Hijab, the head of the opposition High Negotiations Committee, on Twitter.
Salem Muslet, an HNC spokesman, said de Mistura's comments were "unacceptable" and showed a "disregard for the ability of the representatives of the Syrian people".
Muslet rejected the suggestion that the opposition was responsible for the delay in talks, which he said was "not in the interests of the Syrian people".
The delay was "a response to the demands of the regime's allies", he argued.
He also asked whether de Mistura would "intervene" to form the delgation of President Bashar al-Assad.
سایت تابناک از انتشار نظرات حاوی توهین و افترا و نوشته شده با حروف لاتین (فینگیلیش) معذور است.