Major General Robert Mood left his hotel in Damascus on Thursday, July 19 to fly to Geneva after a 90-day UN peace monitoring mission to Syria ended, Reuters reported.

The observers' mandate ends on Friday, but the United Nations' 15-nation Security Council is set to decide later on Thursday whether it should be extended for 45 days.

"I leave satisfied that I, and some 400 brave women and men, have done our best, under very challenging circumstances," Mood, who led the UN mission, told a news conference in the Dama Rose hotel.

"For the sake of the Syrian people we need effective leadership from the Security Council and genuine unity around a political plan that meets the aspirations of the Syrian people and that is accepted by the Parties," Mood said.

"Government and opposition must be willing to make the necessary concessions and sit at the negotiating table," he added, saying there was no hope for the crisis to be resolved through fighting.

Separately, UN Secretary-General Ban Ki-moon said on Thursday he was alarmed by the intensifying violence in Syria, saying he strongly condemned the bombing in Damascus on Wednesday that killed the Syrian defense minister and President Assad's brother-in-law.

Mood's farewell speech came as the UN Security Council was preparing to vote later on Thursday on a Western-backed resolution that threatens Syrian authorities with sanctions and is aimed at ending the 16-month conflict.