The two main opposition groups from inside Syria will take part in peace talks with the regime set for early April in Moscow, the two parties told AFP Friday.
Head of the Building the Syrian State Party and known dissident Louay Hussein announced his party would attend the talks at the invitation of regime-backer Russia.
Despite a travel ban pending an ongoing court case, Hussein said he hoped he could attend the talks alongside party representatives Mona Ghanem and Anas Judeh.
Hassan Abdel Azim, head of the National Coordination Committee for Democratic Change (NCCDC), will also head to Russia with two other leaders from his party.
Although members of the two parties had taken part in a round of discussions in January in an individual capacity, this is the first time they would take part officially as opposition parties.
The Western-backed opposition in exile has declined Moscow's invitation, saying that the talks would seek to bolster the regime of President Bashar al-Assad.
According to NCCDC spokesman Monzer Khaddam, "the agenda (in Moscow) will be based on humanitarian issues and if the regime responds favorably, we will be able to discuss reactivating Geneva."
The first round of Geneva talks took place in 2012 between Russia and opposition-backer the United States, and the second round took place in 2014 between the regime and opposition.
"The Russians are more serious now than their first session," Hussein told AFP. He was released on bail after three months in detention, but is still accused of having "weakened national sentiment" and is banned from leaving the country.  
"This session is a preparatory meeting... I hope that the regime will lift this ban so that I can go to Moscow," Hussein said. The verdict for his case is to be announced April 29.
More than 215,000 people have been killed since Syria's conflict began in March 2011.