The United Nations special envoy for Syria says U.N.-sponsored political talks between the Assad regime and opposition groups have been postponed from Feb. 8 to Feb. 20.

Staffan de Mistura told reporters Tuesday after briefing the Security Council that the talks are being delayed to try to solidify the Dec. 30 cease-fire agreement, to give the regime a chance "to become seriously engaged in concessions" and to give the opposition time to unify its delegation.

De Mistura said invitations will be issued around Feb. 8, and if the opposition isn't united by that date he will select the delegation and ensure that it is as inclusive as possible and include women, which has not previously been the case.

The U.N. envoy said the cease-fire "broadly quite effectively is working in Syria."