The U.N. Security Council on Wednesday endorsed international emissary Kofi Annan’s diplomatic plan to stop violence in Syria, crack open the door to humanitarian relief and prod the Syrian government and opposition into talks on a political settlement.

The endorsement constituted a rare show of unity by the Security Council on the crisis in Syria, where more than 8,000 people have been killed since President Bashar al-Assad’s government launched a crackdown on protesters a year ago. It also lends additional muscle to the efforts of Annan, who serves as the joint U.N.-Arab League envoy to Syria, to persuade Assad to accept his terms.

A Security Council statement is less forceful than a legally binding resolution but often serves as a first step toward tougher action.

The United States and its Arab and European partners have pressed for passage of an Arab League proposal that would have required Assad to yield considerable powers to a transitional government. But Russia, backed by China, recently vetoed a resolution endorsing that plan, insisting that the Syrian government should remain central to any negotiations on a political settlement in Syria.

To secure Russian support, the council’s Western and Arab powers were forced to offer several concessions. A council statement, as a result, includes no condemnation of Syria, no specific timetable for a political transition and a watered-down threat of possible action against Syria if it fails to comply with the Annan plan.

At the last minute, the statement’s sponsors also stripped out a U.S. amendment demanding that Syria immediately allow U.N. humanitarian workers unimpeded access to civilians.

Still, Russia’s and China’s support for the statement represents a considerable blow to Assad, who has counted on the council’s disunity in rebuffing previous diplomatic entreaties.

U.S. Ambassador Susan E. Rice characterized the council’s action as a “modest step” but added that it offered the greatest hope of reuniting the 15-nation council.

“As the council recognized,” Rice said, “Annan’s proposal is the best way to put an end to the violence, facilitate much-needed humanitarian assistance and advance a Syrian-led political transition. We urge the Syrian authorities to respond swiftly and positively.”

The council’s action comes less than a week after Annan, a former U.N. secretary-general, appealed to the Security Council in a closed-door session to rally behind his initiative and reflects mounting concern that the worsening violence could descend into a protracted civil war.

In continued violence Wednesday, activist groups said 52 people were killed across Syria, including at least 25 who died in shelling by government forces against the Homs neighborhood of Khaldiyeh, a rebel stronghold. The figures could not be independently verified, but the reports of violence are consistent with indications that the government is still pressing an offensive to crush the year-long revolt.

There were also reports of firefights in two Damascus suburbs, Harasta and Arbeen, between government forces and rebel fighters.

Meanwhile, in a statement posted on a jihadist Web site, a newly established Islamist group called the al-Nusra Front claimed responsibility for an unspecified number of recent bombings, including two attacks in Damascus over the weekend that targeted branches of the Syrian security services.

Wednesday’s U.N. statement endorses a six-point plan that Annan presented this month to Assad and that calls on the Syrian leader to halt his military crackdown and appoint an envoy to participate in talks with the opposition.

The plan urges Assad to “commit to stop the fighting and achieve urgently an effective United Nations supervised cessation of armed violence” and to join in a “Syrian-led political process” that will “address the legitimate aspirations of the Syrian people.”

It would require Assad to “immediately” cease military advances on towns, end the use of heavy weapons, including tanks and artillery, and “begin pullback of military concentrations in and around population centers.”

Annan’s initiative would also require the government to accelerate the release of political prisoners, permit local and international journalists freedom of movement throughout the country and “ensure timely provision of humanitarian assistance” in conflict zones, including a “daily two-hour humanitarian pause” in the fighting to facilitate such assistance.

Annan pledged that he would seek similar commitments from the armed opposition.

Syria has rejected some key provisions of Annan’s plan, arguing that a military pullback from restive towns would leave a security vacuum and demanding that Annan first provide guarantees that opposition fighters will lay down their weapons and that other governments will stop financing or arming them.

“I would characterize the response as disappointing,” Annan told the council Friday, according to a confidential copy of his address, posted by the Arabic-language network al-Hurra’s U.N. reporter. “My mission will be very difficult and faces daunting odds. But I am convinced it can succeed with the united support of the international community behind one mediator effort, with clear goals.”

Correspondent Liz Sly in Beirut contributed to this report.