The United Nations' top envoy for Syria said Wednesday that the next round of talks between the government and opposition will take "in about a month" and no later than early November.

Staffan de Mistura told the U.N. Security Council that both sides should use the next month to create conditions for "meaningful" talks and to participate "without preconditions."

He said Syria's divided opposition should signal "that it wants to speak with one voice and a common platform in genuine negotiations with the government."

De Mistura added that the government has a duty "to genuinely negotiate with the opposition."

He said both sides should show readiness to negotiate on four key issues: local and central governance, a new constitution, U.N. supervised elections and combating terrorism.