The United States has warned Syria to co-operate with an UN-backed peace plan.
Secretary of State Hillary Clinton urged President Bashar al-Assad to "take this path, commit to it, or face increasing pressure and isolation".
The peace plan, put forward by UN envoy Kofi Annan, has now been endorsed by the UN Security Council, with support from Russia and China.
A UN Security Council statement yesterday expressed full support for Annan's plan to end all violence, secure humanitarian access and to facilitate a political transition.
It also says the council will "consider further steps as appropriate", without specifying a time frame.
It is not binding and falls short of a formal resolution.
Meanwhile, UN Secretary General Ban Ki-moon earlier warned of serious repercussions if the crisis in Syria is not resolved.