The opposition also wanted the Government to set out how it would begin releasing prisoners, she said.
Meanwhile, Russian television showed the first group of Su-34 jets landing at a base in the south of Russia. The pilots were greeted by 200 to 300 servicemen, journalists, and their wives and children, waving Russian flags, balloons in red, white and blue, and flowers.
They were mobbed and thrown in the air by the crowd. A brass band played Soviet military songs and the national anthem. Two priests paraded a religious icon.
UN envoy de Mistura called President Vladimir Putin's surprise move a "significant development" towards resolving the conflict which this week passes its fifth anniversary.
Assad's opponents hope Putin's announcement signalled a shift in his support. However, its full significance is not yet clear: Russia is keeping an air base and forces in Syria.
Russian jets were in action against Isis (Islamic State) yesterday. Assad also still enjoys military backing from Iran, which has sent forces to Syria along with Lebanon's Hizbollah.
Russia said last month Assad was out of step with its diplomacy, prompting speculation Putin was pushing him to be more flexible at the Geneva talks, where Assad's Government has ruled out discussion of the presidency or a negotiated transfer of power. AAP