The deputy UN envoy for Syria, Ramzy Ezzeldin Ramzy, said Thursday that progress on the Russian- and the UN-led tracks of peace efforts for the war-torn country were linked.
The United Nations is to host a new round of peace talks on January 25-26 in Vienna, to be followed by a peace congress in Russia's Black Sea resort of Sochi on January 29 and 30.
"There is no doubt that the success of the Vienna meeting will pave the way for the success of the Sochi meeting," Ramzi told a news conference after talks in the Syrian capital.
He said the UN-led talks, to be held in the Austrian capital rather than in Geneva which hosted past rounds, would "focus on the constitutional issue".
Several rounds of talks have failed to end Syria's conflict which has claimed more than 340,000 lives since it broke out in March 2011 with anti-regime demonstrations that were crushed with deadly force.
Both the opposition and the government have said they will take part in next week's Vienna talks.