Syria: diplomatic timeline

- August 18, 2011: US President Barack Obama and Western allies call for President Bashar al-Assad to step down.

- August 27: The Arab League, of which Syria is a member, holds an extraordinary summit on ending the violence.
Efforts by Western powers to obtain a UN Security Council resolution condemning Syria are stymied by Russia and China.

- November 2: The Arab League says it has the agreement of Assad on a plan that would involve an end to the violence and a pullback of belligerent forces, leading to a "conference of national dialogue".Ten days later, however, it votes to suspend Syria's membership in the pan-Arab organisation due to the continued repression. It later also calls on its members to enact sanctions against the regime.

- December 19: After tough negotiations, Syria agrees to receive a delegation of Arab League monitors.

- January 22, 2012: The Arab League agrees on a new plan under which Assad would hand over power to his deputy pending elections.

- January 28: The Arab League acknowledges its observer mission has failed to halt the violence.

- February 24: A group of mainly Western and Arab countries calling themselves the "Friends of Syria" hold a conference in Tunis. However Russia and China, who hold veto power on the UN Security Council, refuse to attend.

- March 21: The Security Council agrees on a plan drafted by its former secretary general, Kofi Annan. The plan calls for a ceasefire, return of troops to their barracks and the opening of talks between the government and opposition.

- April 1: Meeting in Istanbul, Friends of Syria countries extend formal recognition to the Syrian National Council, the main opposition umbrella group.

- April 12: The ceasefire called for under the Annan plan is supposed to come into force -- but violence continues unabated.

- April 14 and 21: The Security Council votes to send first 30 and then 300 observers to Syria.

- June 16: Amid continuing heavy violence, the UN suspends the work of its observer mission, although they remain in the country.

- June 18: Presidents Obama of the United States and Vladimir Putin of Russia meet at a G20 summit and call for "an immediate cessation of all violence."

- June 30: The five permanent Security Council members -- Britain, China, France, Russia and the United States -- plus Turkey and several Arab states, meet in Geneva to discuss a transitional plan for Syria.
The United States says the plan should lead to a Syria without Assad, but Russia and China say that question must be left up to the Syrians.

- July 6: France and the United States push for tougher sanctions on Syria at an international conference of some 100 countries as a top general with close ties to Assad has defected.