Syria's opposition said early Saturday that it will boycott a peace congress in Russia next week, according to its official Twitter account.
"The HNC announces the boycott of the Sochi conference that Russia had invited it to," the tweet in Arabic on the High Negotiations Committee (HNC)'s account said after UN-brokered talks in Vienna.
"Tomorrow (Saturday) there is going to be a press conference by the head of the SNC and he will give you the decision about Sochi, if there is going to be participation or not," said Syrian Negotiations Commission (SNC) spokesman Yahya al-Aridi.
The comments came at the end of two days of what Aridi called "tough talks" hosted by the United Nations in Vienna.
Like in eight previous rounds in Geneva, the SNC and Syrian government representatives held separate talks with UN envoy Staffan de Mistura but the two delegations did not meet face to face.
Russia, which has helped turn the Syrian war in favor of its ally President Bashar al-Assad, has invited 1,600 people to the Black Sea resort of Sochi to begin hammering out a new constitution for post-war Syria.
The meeting is also backed by Iran and Turkey, two key players in the complex and devastating seven-year-old conflict, but viewed with skepticism by the opposition and Western countries.
They fear it will sideline the UN track and carve out a settlement in favor of Assad.
The United Nations is still considering whether to attend the Sochi conference and will make a decision based on the outcome of the Vienna meetings, spokesman Farhan Haq said Friday.
"We are evaluating the situation as of the end of the talks," Haq told reporters at UN headquarters in New York.
"Once they have happened, Mister De Mistura will evaluate what the situation is and we can then evaluate from there what our presence in Sochi may or may not be."
Aridi's comments came ahead of a scheduled news conference by de Mistura in the Austrian capital late Friday.