"The negotiations will be very difficult," Kerry said at a news conference in Paris with his Qatari counterpart.
Kerry also said on Sunday he was confident that Syrian opposition groups would attend peace talks in Switzerland later this month."Personally, I'm confident that the Syrian opposition will come to Geneva," Kerry told reporters in Paris.He said attendance was a "test of the credibility of everybody". "That's why I am confident they will be there," he said.The Western-backed Syrian National Coalition, which groups various Syrian opposition groups working from abroad, is due to decide on January 17 whether it will attend the talks, scheduled for January 22.Herb Keinon and Reuters contributed to this report.