The new UN / Arab League envoy to Syria says he urgently needs to clarify what support the United Nations can give him.
Lakhdar Brahimi of Algeria is to take over from Kofi Annan, who has complained that divisions within the Security Council hampered his work.
Russia and China have vetoed sanctions against the Syrian government, while the United States, Britain and France favour tough action.
Mr Brahimi says he is acutely aware of the problem.
The UN on Thursday ended to its military observer mission in Syria.
Mr Brahimi, 78, has held a long series of high-profile diplomatic posts, notably as the UN's top envoy in Afghanistan in 1996-8 and 2001-4.
Analysts say he is seen as independent of the major powers.
The United States, Russia and Syria have all welcomed his appointment. Mr Annan failed to achieve a real ceasefire.
Mr Brahimi will have a new title, Joint Special Representative for Syria. Diplomats said this is to distance him from Annan