U.S. Secretary of State John Kerry says he is confident the Syrian opposition will attend this month's peace talks in Geneva.
Kerry said after a foreign ministers meeting in Paris Sunday that coming to the talks would be a test of credibility for all parties.
The Western-backed Syrian National Coalition has said it will decide by the end of the week whether to attend the January 22 talks.
Opposition leaders have expressed misgivings about sitting at the negotiating table with representatives of Bashar al-Assad's government.
Assad has said the Syrian government will attend the talks, but has said that only the Syrian people can decide the country's future.
French Foreign Minister Laurent Fabius said at the Friends of Syria meeting Sunday that the goal of the talks is setting up a transitional government for Syria "with full executive powers."