Beirut / AFP A ceasefire brokered by Moscow and Washington is due to take effect in Syria at sundown on Monday, the latest bid to end fighting between regime forces and moderate opposition.
There have been multiple previous attempts since the conflict erupted in 2011 but all have ended in failure.
Here are some of the efforts since 2011:
Photo: Syrian men carrying babies make their way through the rubble of destroyed buildings following a reported air strike on the opposition-held Salihin neighborhood of the northern city of Aleppo, on September 11, 2016.
Arab initiatives
November 2, 2011: The Arab League says it has reached an agreement with Syria to end the fighting, free detainees and withdraw troops from cities.
No clauses are respected. The League later suspends Syria and approves unprecedented sanctions.
In early 2012, Damascus formally rejects the plan and says it is determined to crush the rebellion.
Photo: Arab foreign ministers attend an emergency meeting on Syria at the Arab League Headquarters in Cairo, November 12, 2011.
Annan plan
April 12, 2012: UN-Arab League envoy Kofi Annan manages to establish a truce, but it collapses within hours.
Photo: In this photo released by the Syrian official news agency SANA, Bashar Assad, right, meets with Kofi Annan, the United Nations special envoy to Syria, in Damascus, Syria, on Saturday March 10, 2012.
Geneva I
June 30, 2012: An "action group" meeting in Geneva says it has reached agreement on a Syrian transition of power.
But those present - Arab states, Britain, China, France, Russia, Turkey and the United States - have different interpretations of the deal.
Washington says it marks the start of a "post-Assad" period, referring to Bashar al-Assad. Beijing and Moscow maintain that it is up to the Syrians to determine their own future.
Photo: UN-Arab League special envoy and former UN Secretary General Kofi Annan (R) sits next to Russian Foreign Minister Sergei Lavrov (L) during a meeting of the Action Group for Syria at the United Nations office, in Geneva, on June 30, 2012.
Chemical weapons deal
September 14, 2013: Russia and the United States agree to dismantle Syria's chemical arsenal after an attack - widely blamed on Assad's regime - kills hundreds of people near Damascus.
The last-minute deal averts threatened US-led air strikes against the regime, which denies carrying out the attack.
Photo: UN convoy of vehicles, carrying the UN team of inspectors, crossing into Lebanon from Syria, at the Lebanese border crossing point of Masnaa, eastern Bekaa valley, Lebanon, Sept. 27, 2013.
October 11, 2013: The Organisation for the Prohibition of Chemical Weapons (OPCW), headed by Turkish diplomat Ahmet Üzümcü won the Nobel Peace Prize on October 11, 2013 for its efforts in reaching the deal. Set up in 1997 to eliminate all chemicals weapons worldwide, its mission gained critical importance this year after a sarin gas strike in the suburbs of Damascus killed more than 1,400 people in August.
Photo: OPCW Director General Ahmet Üzümcü, speaking during a news conference in The Hague October 9, 2013.
Geneva II
January 22-31, 2014: The Russia-backed Syrian regime and U.S.-supported opposition figures hold talks in Switzerland without results.
February 15: UN mediator Lakhdar Brahimi, who replaced Annan, ends the talks. He resigns on May 13 after more than 20 months of fruitless efforts and is replaced in July by Staffan de Mistura.
Photo: (From L) UN-Arab League envoy for Syria Lakhdar Brahimi, EU foreign policy chief Catherine Ashton, and UN Secretary General Ban Ki-Moon pose prior to a meeting on January 21, 2014 at the United Nations offices in Geneva ahead of the Geneva II conference in Montreux.
Russian offensive/Vienna talks
October 30, 2015: A month after Russian air strikes begin in Syria at the request of Damascus, 17 countries including Russia, the United States and for the first time Iran, meet in Vienna.
The regime and opposition are absent from the talks, which break up amid deep disagreement over Assad's fate.
November 14: World diplomats gathered in Vienna agree on a fixed calendar for Syria's future but remain sharply at odds over Assad.
Photo: US Secretary of State John Kerry (CL) and Russian Foreign Minister Sergei Lavrov (CR) chat before talks with 17 nations, the European Union and United Nations at the Hotel Imperial on October 30, 2015 in Vienna, Austria.
UN resolution passed
December 18, 2015: For the first time, the UN Security Council unanimously adopts a plan for a political solution, including negotiations between the opposition and the regime as well as a ceasefire. The text provides for a transitional government within six months and elections within 18 months.
Photo: Foreign Minister of Russia Sergei Lavrov (L) and US Secretary of State John Kerry shake hands after a news conference after a UN Security Council meeting on Syria at the United Nations in New York on December 18, 2015.
Failure in Geneva
February 3, 2016: UN-sponsored talks between the opposition and government are suspended amid a regime offensive against the rebels in the Damascus region, backed by Russian air power.
Photo: Syria UN envoy Staffan de Mistura (L) meets representatives of the Syrian regime, at the opening of Syrian peace talks at the United Nations offices in Geneva on January 29, 2016.
'Cessation of hostilities'
February 27, 2016: A U.S.-Russia brokered "cessation of hostilities" comes into force. Accepted by the regime, the opposition and PYD forces, it excludes the main extremist factions including Daesh and al Qaeda linked Nusra Front.
Photo: De Mistura speaks during a press conference about the beginning of a cessation of hostilities in Syria and the next talks scheduled in Geneva between the regime and the opposition, at the European headquarters of the United Nations, in Geneva, Switzerland, late Friday, Feb. 26, 2016.
Indirect negotiations
March 14-24: A first round of indirect negotiations between the regime and opposition takes place under UN auspices, without making progress.
April 13: Peace talks open in Geneva. On April 18, the opposition postpones its "formal participation" in the talks in protest over escalating violence.
Photo: Syrian chief negotiator Bashar al-Jaafari (L), Ambassador of the Permanent Representative Mission of the Syria to UN New York (L) , and UN Special Envoy of the Secretary-General for Syria, Staffan de Mistura (R), wait prior a new round of negotiations between the Syrian government and UN, at the European headquarters of the UN in Geneva, Switzerland, Monday, March 14, 2016.
New Russian-American accord
September 9: U.S. and Russian diplomatic chiefs John Kerry and Sergei Lavrov reach a deal on a ceasefire and possible unprecedented cooperation on military action against jihadists.
The regime accepts the ceasefire but the opposition High Negotiations Committee seeks "guarantees" on its implementation just hours before it is due to take effect at sundown on September 12.
Powerful opposition group Ahrar al-Sham rejects the truce.
Photo: (L -R) United Nations Special Envoy for Syria Staffan de Mistura, US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov attend a press conference after meetings to discuss the Syrian crisis early on September 10, 2016, in Geneva.
