Russia and China Thursday vetoed a resolution renewing the mandate of the U.N. Supervision Mission in Syria (UNSMIS) that also threatened sanctions against Syrian authorities if they did not withdraw troops from population areas and stop using heavy weapons within ten days. Eleven of the Security Council members voted for the resolution while two - South Africa and Pakistan - abstained. The mandate for UNSMIS expires Friday, and the observer force - which was sent to Syria in April - will have to withdraw this weekend, unless the council drafts another resolution that gets the support of the five veto-wielding permanent members and support of at least four more countries before Friday. Earlier Thursday, the head of the U.N. mission in Syria, Major General Robert Mood, spoke to reporters in Damascus prior to leaving for Geneva. "I leave satisfied that I, and some 400 brave women and men, have done our best, under very challenging circumstances," Mood said at a news conference. Mood announced ahead of the vote that he was stepping down as head of UNSMIS.