The Syrian opposition council has yet to be officially informed of U.N. plans to hold a new round of peace talks on March 9 and no serious discussions can begin before detainees are freed and blockades are lifted, an opposition official said on Tuesday.

Riad Nassan Agha, a member of the opposition High Negotiations Committee, said the opposition would study the call for talks based on developments on the ground, adding that the opposition had only heard of the March 9 date in the media.

He said he did not see "good implementation" of humanitarian clauses in a U.N. Security Council resolution the opposition has demanded be carried out for Syria peace talks to begin. He added that U.N. envoy Staffan de Mistura appeared to be "in a hurry".

"Something must be realised on the ground regarding implementation of the Security Council resolution for negotiations to begin seriously," Agha told Reuters by telephone. "And so far it does not seem that there are indications of this good implementation."

He also described a cessation of hostilities as "fragile and weak", adding that there were many violations by government forces. "Therefore I do not know what new developments may happen between now and March 9."