A senior European official, briefing reporters on the Security Council deliberations, said supporters of the British proposal were adamant in their view that any new Security Council resolution must have Chapter 7 coercive pressure. “We cannot do business as usual,” the official said.

Russia has put forth a competing proposal: to extend the military observer mission under a slightly broader mandate, allowing it some political role.

Mr. Lavrov repeated Russia’s position that both the government and the opposition should be pressured, although the United Nations has pushed the point that the government, as the dominant party, needs to act first.

“Any violence deserves condemnation,” Mr. Lavrov said. “But condemnation alone will not suffice. Pressure should be put on the regime and on the opposition in order to end the violence there.”

Mr. Lavrov appeared to lay the groundwork for another Russian veto — its third — of a resolution addressing the violence in Syria. “If our partners decide to block our resolution at any cost, the U.N. mission will not have a mandate and will have to leave Syria,” he said. “That would be lamentable.”

He also expressed concern for the fate of members of minorities, including Orthodox Christians, if an opposition dominated by Sunni Muslims gained power. But Christians with long experience in Syria have pointed out that Russia did nothing to save the 150,000-member Christian community in the city of Homs; most fled in the face of devastating government attacks.

On Monday, Damascus endured some of the heaviest fighting there since the uprising began in March 2011. Although there have been periodic clashes, opposition activists said this was the most sustained combat to date, with the government using weapons like tanks and mortars, which it had avoided in Damascus in its quest to present life there as normal.