The U.N. envoy for Syria plans to host separate meetings with government and opposition delegations Jan. 25-26 in Vienna, citing "logistical reasons" for a decision not to hold a new round in Geneva.

The office of Staffan de Mistura sent invitations Wednesday for the meetings, which will focus on constitutional issues and will not amount to a full "round" of broader talks like those in Geneva over the last two years.

Switzerland is facing security demands and lodging issues with the Davos conference next week. De Mistura wants to see the two sides before possible Russian mediation in Sochi.

Last month, de Mistura wrapped up the eighth round of largely ineffective talks by saying he was "disappointed" that no progress had been made. He accused Syria's government of setting preconditions.