"He is still in intensive consultations on the way forward," spokeswoman Jessy Chahine told a news briefing in Geneva, Reuters reported.
"He is of course consulting with his team and other relevant stake-holders."
The United States broke off talks with Russia on Monday on implementing a ceasefire agreement in Syria and accused Moscow of not living up to its commitments under the Sept. 9 deal to halt fighting and ensure aid reached besieged communities.
Moscow says it does not accept responsibility for the breakdown in cooperation, and says it has done everything to sustain the peace process, including implementing a 72-hour ceasefire late last month that should have ensured the delivery of humanitarian aid to Aleppo, the site of the most intense fighting between government forces and opposition factions.