By Louis Charbonneau and Michelle Nichols
UNITED NATIONS (Reuters) - The United Nations' four-month-old observer mission in Syria will withdraw from the country next week, diplomats and U.N. officials said on Thursday, yet another blow to the world body's efforts to broker an end to the conflict.
"The mandate of UNSMIS is over on the 19th of August ... UNSMIS will fade out," said French U.N. Ambassador Gerard Araud, who is the president of the Security Council for the month of August.
Speaking to reporters after a closed-door meeting of the council, he said conditions for renewing the mandate of the observer mission in Syria, known as UNSMIS, had not been met.
The death of UNSMIS cast further doubt on the viability of outgoing international mediator Kofi Annan's moribund six-point peace plan for Syria. Some Western diplomats describe that plan as doomed, while others suggest it could still be salvaged.
Annan, a former U.N. secretary-general and Nobel Peace Prize laureate, will step down on August 31. He has criticized the 15-nation council for failing to agree on steps that could have pressured Syria's government and rebels to stop fighting.
Veteran Algerian diplomat Lakhdar Brahimi has agreed to replace Annan as the international mediator on Syria but with an altered mandate, U.N. sources said on Thursday.
Envoys said he has demanded "strong support" from the Security council and a source familiar with the situation said that Brahimi would not continue with Annan's "failed approach.
Russian U.N. Ambassador Vitaly Churkin said Annan's peace plan was still relevant. He added that the permanent Security Council members - Russia, China, the United States, France and Britain - and key regional players would meet on Syria in New York on Friday morning to discuss the crisis.
"We're sorry that the UNSMIS mandate is coming to an end," Churkin told reporters. "We believe that those members of the council who insisted that UNSMIS can't continue did not really show commitment to ending hostilities and to working toward a political settlement in Syria."
Russia had repeatedly called for the monitors to remain in Syria. But the United States opposed keeping them in the country as long as Syrian President Bashar al-Assad's forces escalated their 17-month-old onslaught against an increasingly well armed, experienced and determined opposition.
Moscow, with the aid of Beijing, has vetoed three resolutions criticizing and threatening sanctions against Syria. That has led to an impasse on the council, Western envoys say. Moscow blames the deadlock on Washington and its allies, saying they are supporting the rebels in pursuit of "regime change."
'THE PATH OF WAR'
The Security Council said last month it would only renew the mandate of UNSMIS, which was deployed in April to monitor a truce that never took hold, if the world body confirmed a "cessation of the use of heavy weapons and a reduction in the level of violence by all sides sufficient" for it to operate.
In an August 10 letter to the Security Council, U.N. Secretary-General Ban Ki-moon said this has not been achieved and the mission "has not been able to exercise its key functions of monitoring the cessation of violence."
Deputy U.N. peacekeeping chief Edmond Mulet told reporters that the mission's legal mandate would expire at midnight New York time on Sunday and the last military observers would be out of Syria by August 24.
"It is clear that both sides have chosen the path of war, open conflict and the space for political dialogue and cessation of hostilities and mediation is very, very reduced at this point, but that doesn't mean we should not be engaged in that," Mulet told reporters after privately briefing the council.
"The situation on the ground is extremely difficult," he said. "But the fact that it's difficult doesn't mean that we should not face that challenge of trying to open those political spaces in the future."
The mission's initial 300 unarmed observers suspended most of their activity on June 16 because of increased risk from rising violence. UNSMIS now has over 70 civilian staff working issues such as aid access and monitoring human rights abuses.
Mulet said UNSMIS would be replaced with a U.N. political liaison office with 20 to 30 people, including military advisers and human rights, aid and de-mining experts.
Churkin said Friday's meeting of the so-called "Action Group" on Syria in New York would take place at 11:00 a.m. EDT. In addition to Russia, China, the United States, Britain and France, it will include regional players like Turkey, Qatar, Kuwait and Iraq.
Saudi Arabia and Iran, which did not participate in a ministerial meeting of the group in July, will not take part in Friday's ambassadorial level session, Churkin said. The group's July meeting ended with an agreement to revive Annan's peace plan and urged the government and rebels to stop fighting.
Syria says Qatar, Saudi Arabia and Turkey are arming the rebels. Washington and its allies say that Russia, Assad's chief arms supplier, and Iran are propping up the Syrian government by providing it with military support and munitions.
(Editing by Xavier Briand and Vicki Allen)