Sergey Lavrov, speaking on a trip to Armenia today, said some of the participants in the talks have kept pushing for Assad to step down, in what he described as a "simplistic approach."
The first round of Vienna talks on Oct 30 left open the thorny question of when Assad might leave power.
Lavrov said the talks should focus on reaching consensus on who should represent the Syrian opposition and who should be considered extremists. He said the Organization of Islamic Cooperation and the Arab League should be invited to join the following round of Vienna talks.