Russia says it will not heed the demands of the West and vote for sanctions on Syria to try to end the violence there.

At the United Nations Security Council, Britain, France, Germany and the United States said Thursday that sanctions must be invoked against Damascus within 10 days unless the Syrian military stops using heavy weapons against opposition forces.

Security Council members plan to vote on the resolution later Thursday.

Russia says the Council should pass an alternate resolution that would simply extend the mandate of the U.N. observer mission in Syria for another three months.

Meanwhile, Syrian Ambassador to Iraq Nawaf Fares has defected and joined the opposition to President Bashar al-Assad. Fares is urging members of Syria's military to join him, saying there is no honor in killing one's own people.

Fares is the highest-ranking Syrian official to switch sides since the uprising against Mr. Assad's regime began 16 months ago.

White House spokesman Jay Carney says those in the military and government close to Mr. Assad are assessing his chances of staying in power and deciding to abandon him in favor of the Syrian people.