The U.N. envoy for Syria says the declaration of so-called de-escalation zones has been "so far positive," and hailed a Russian initiative to help bring aid to besieged Syrians.

Staffan de Mistura set no date for new peace talks in Geneva. He said "short" talks might be possible next month, while expressing hope for "substantial" talks in October. He also cited divisions among opposition factions.

The envoy said 50 trucks reached the besieged town of Douma northeast of Damascus on Thursday, the first aid convoy there since May. That resulted from an Aug. 2 letter he received from Russian Defense Minister Sergei Shoigu promising Russian military "observation points" to facilitate movements within Syria.

U.N. aid official Jan Egeland said the number of "quiet zones" is increasing in Syria.