Syria's main Western-backed opposition coalition is set to vote Friday on whether to attend next week's peace talks in Geneva.
The Syrian National Coalition's meeting in Istanbul comes amid intense U.S. pressure for the opposition to attend the conference, which is aimed at forming a transitional government.
Secretary of State John Kerry said Thursday the talks are the "best opportunity for the opposition to achieve the goals of the Syrian people and the revolution."
"It is about establishing a process essential to the formation of a transition governing body with full executive powers established by mutual consent. That process, it is the only way to bring about an end to the civil war that has triggered one of the planets most severe humanitarian disasters and which has created the seeding grounds for extremism."
Kerry said the leader of any transitional government would have to be approved by all sides, meaning Syrian President Bashar al-Assad would likely be excluded.
Opposition leaders so far have refused to attend talks without a prior commitment that President Assad will step down.
Syrian Foreign Minister Walid al-Moallem confirmed Friday that Damascus will attend the January 22 conference.
"As I already confirmed yesterday, the Syrian delegation will go to Geneva, as we believe that a peace settlement is the only way out of the conflict in Syria."
Speaking in Moscow after meeting with his Russian counterpart (Sergei Lavrov), Moallem also said he is ready to exchange lists with rebel forces on a possible prisoner exchange and that he has handed Russia plans for a cease-fire in Aleppo, Syria's biggest city.
But Moallem also shot back at Washington, which he said was "supporting terrorist groups" in Syria's civil war.
The Syrian government considers all rebel forces to be terrorists, and has tried to shift the focus of the proposed peace talks from forming a new government to fighting extremism.
Kerry said Thursday the U.S. also is concerned about the rise of extremism in Syria, but insisted Damascus is to blame for the unrest that has left over 120,000 people dead.