UN Special Envoy for Syria Staffan de Mistura arrives at a meeting with government delegation during Syria peace talks in Geneva, Switzerland March 31, 2017. REUTERS/Fabrice Coffrini/Pool

GENEVA (Reuters) - Representatives of Syria’s warring sides went into considerable detail on the substance of the agreed agenda during a round of Syria talks that ended on Friday, and are keen to return for another round, U.N. mediator Staffan de Mistura said.

“I believe I can speak on behalf of all who participate that we must maintain this incremental progress on the political process, even if only incremental,” he told reporters.

“I cannot deny that there are serious challenges and I am not seeing this immediately developing into a peace agreement, no doubt about that.”