"Russia will ask for a delay, but we will be voting today," British Ambassador Mark Lyall Grant said.
"Now, it's over," agreed French Ambassador Gerard Araud. "This text is simple. We support the Arab peace plan. Nothing more, nothing less and we vote today."
Russian Ambassador Vitaly Churkin told reporters before entering the meeting that he had asked for a meeting of all Security Council ambassadors before any vote was taken, but provided no other specifics. The council began meeting shortly after 10 a.m. (1500 GMT) behind closed doors.
It was not immediately clear if the meeting would be opened later, or when a vote might be called.
In Germany, Lavrov said the resolution makes too few demands of anti-government armed groups, and that Moscow remains concerned that it could prejudge the outcome of a national dialogue among political forces in Syria.
Syria has been a key Russian ally since Soviet times and Moscow has opposed any U.N. call that could be interpreted as advocating military intervention or regime change.
President Barack Obama urged the Security Council to take a stand against Assad's regime and back the resolution.
"The international community must work to protect the Syrian people from this abhorrent brutality," Obama said in a statement issued by the White House.