Nasr al-Hariri (2nd L), head of the Syrian opposition delegation, arrives for Syrian peace talks in Vienna, Austria, on Jan. 25, 2018. Syrian peace talks organized by the United Nations (UN) resumed here on Thursday, days before Russia-sponsored peace talks scheduled to take place in Russia's Sochi. (Xinhua/Pan Xu)

VIENNA, Jan. 25 (Xinhua) -- Syrian peace talks organized by the United Nations (UN) resumed here on Thursday, days before Russia-sponsored peace talks scheduled to take place in Russia's Sochi.

UN special envoy for Syria Staffan de Mistura said he was optimistic about the "critical" talks taking place in the Austrian capital.

However, the Syrian opposition is still to decide whether it will participate in the Sochi peace talks, to be held by the end of this month.

Syrian opposition leaders added they would make that decision in the next two days in Vienna.

There has been no information yet if the Syrian government would talk to the opposition in Vienna directly to accelerate the process.

Syrian peace talks have made little progress in the past few rounds in Geneva, and in Vienna.

Before the meeting, French Foreign Minister Jean-Yves Le Drian said that talks in the capital of Austria were the "last hope" for reaching a political solution.