* Rice: Some countries skeptical about Syrian commitments
* Unclear how Russian reacting to Annan's announcement
UNITED NATIONS, April 2 (Reuters) - U.N.-Arab League envoy Kofi Annan told the U.N. Security Council on Monday that Syria has accepted an April 10 deadline for ending military operations, with the opposition under pressure to cease fighting within 48 hours of that, envoys said.
But Western diplomats expressed skepticism about the credibility of Syria, which has repeatedly promised to end attacks but has pressed ahead with a year-long assault on anti-government activists that has brought the country to the brink of civil war.
"Mr. Annan reported that the Syrian Foreign Minister sent him a letter yesterday in which he said that the Syrian military will begin immediately and by April 10 will complete the cessation of all forward deployment and use of heavy weapons and will complete its withdrawal from population centers," U.S. Ambassador to the United Nations Susan Rice told reporters.
Speaking after Annan addressed a closed-door meeting of the 15-nation council via video link, Rice added that Annan's deputy Nasser al-Kidwa "has also had constructive exchanges with the opposition to urge them to cease their operations within 48 hours of a complete cessation of government hostilities."
Rice added that several council members had "expressed concern that the government of Syria not use the next days to intensify the violence and expressed some skepticism about the bona fides of the government in this regard."
Syria's Ambassador to the United Nations, Bashar Ja'afari, confirmed that Damascus accepted the April 10 deadline but said the government wants the opposition on board.
"The Syrian government is committed but we are expecting Mr. Kofi Annan and some parties in the Security Council also to get the same kind of commitments from the (opposition)," he told reporters. "A plan wouldn't be successful unless everybody is committed to it."
"It's by common accord between our minister and Mr. Kofi Annan," he said when asked who suggested the April 10 deadline.
CEASEFIRE MONITORING MISSION
So far there has been no sign of Syrian President Bashar al-Assad keeping his promise to implement Annan's six-point peace plan, which calls for an end to violence and political dialogue between the government and opposition aimed at a "political transition" for the country.
There is "no progress on the ground" so far, a diplomat inside the meeting told Reuters in a summary of Annan's remarks.
Despite the lack of progress, Annan suggested there may be the beginnings of a plan to end the year-long conflict and he urged council members to "begin consideration of deployment of an observer mission with a broad and flexible mandate," a diplomat said.
Rice said that "in general council members expressed a willingness to consider Mr. Annan's plan for a monitoring mission if indeed a cessation of violence is achieved."
The U.N. peacekeeping department has already begun contingency planning for a U.N. ceasefire monitoring mission that would have 200 to 250 unarmed observers. Such a mission would require a Security Council resolution.
It was not immediately clear how Russia was responding to Annan's suggestions. Russian Ambassador Vitaly Churkin left the council without speaking to reporters.
Russia and China vetoed two council resolutions condemning Assad's assault on pro-democracy demonstrations, which were inspired by other "Arab Spring" uprisings across the Middle East and North Africa.
The United Nations says Syrian soldiers and security forces have killed more than 9,000 people over the past 12 months. Damascus says rebels have killed 3,000 troops and police.