The U.N. Security Council unanimously adopted a resolution to boost humanitarian access in Syria that threatens to take "further steps" in the case of non-compliance, demands cross-border aid access and condemns rights abuses by the Syrian government and opposition armed groups. (Eduardo Munoz/REUTERS)

The U.N. Security Council on Saturday unanimously approved a resolution demanding that Syria immediately halt attacks on civilians and allow unfettered humanitarian access to besieged areas and across neighboring borders, threatening unspecified “further steps” if the government does not comply.

The action marked the first time Russia has agreed to a binding resolution against Syrian President Bashar al-Assad’s regime since the conflict in his country began nearly three years ago. China, which vetoed three previous resolutions along with Russia, joined in approving the measure.

The vote came after lengthy negotiations over the past week. To secure Russia’s agreement, sponsors of the resolution agreed to include specific demands for opposition fighters to cease their own violations of human rights and international law, to condemn terrorism and to drop a demand that government violators be referred for prosecution to the International Criminal Court.

Russia had sharply criticized the initial measure. But U.S. officials said they were prepared to push it regardless to force Moscow — currently in the international spotlight during the Sochi Olympics — to take a position on increasingly horrifying reports of human carnage in Syria.

Secretary of State John F. Kerry said the resolution “could be a hinge-point in the tortured three years of a Syria crisis bereft of hope.” But he said that while it is a resolution of “concrete steps,” they were only first steps and that demanding access means little without full implementation.

The United States and other strong advocates acknowledged a lack of specific enforcement tools in the resolution, which instructs U.N. Secretary General Ban Ki-moon to report back on compliance within 30 days. But U.S. Ambassador Samantha Power and others noted that the threat of “further steps” is far stronger than language in previous, vetoed measures and said it commits the council to take action.

“A resolution is just words,” Power said. “It is implementation that matters, and that’s what we are starting to measure right now.” Language committing the council to further actions, she said, is a “significant hook, a significant commitment by the parties on the Security Council.”

Britain referred specifically to possible future action under articles of the U.N. charter that authorize the use of armed force. Speaking in London, British Foreign Secretary William Hague said that “we will not hesitate to return to the Security Council if the Assad regime fails to meet the demands in this resolution.”

While the resolution includes condemnation of al-Qaeda and “affiliated groups” active in Syria, the final version dropped earlier references to Lebanese-based Hezbollah and Iran’s Quds Force, both of which have been involved in the fighting on the government’s side.

In a statement after the vote, Russian Ambassador Vitaly Churkin described the two sides as equally responsible for the situation in Syria and said that genuine opposition forces should “pool efforts with the government” to fight against terrorist involvement.

But the United States and others made clear that they see the resolution as directed primarily at the Assad government. Syria’s humanitarian crisis is not “the inevitable consequence of war,” Power said. “I say it is the result of willful actions by specific individuals” in the “Syrian regime led by Bashar al-Assad,” she said, adding, “I refer to him and his security forces.”

Chiding the council’s members for their inability to come together for the past three years, Power said “it is a gross understatement to say it should not have taken this long.”

While Churkin and Syria’s U.N. representative hailed recent reports of government-initiated cease-fires and aid deliveries in long-besieged areas south of Damascus, other diplomats used their statements to blame the government for what Ban called a “profoundly shocking” and rapidly worsening situation in which millions have been driven from their homes and more than 100,000 have been killed.

In his speech to the council, Syrian Ambassador Bashar Jaafari charged “some members” with hypocrisy in providing arms and other assistance to opposition forces across the same international borders they now say should be opened for humanitarian aid.

“Violence has reached almost the absurd, the illogical and surreal. This is true,” Jaafari said. “But the question remains: Why is this happening in Syria, and why this unjustified silence toward all forms of crude intervention?”

For “some” council members, he said without naming names, “this is the diplomacy of hyenas and not the diplomacy of international humanitarian law.”

The United States and its European and Arab partners have newly agreed to coordinate their efforts to provide arms and training to “moderate” opposition fighters to increase their prowess against both Assad’s forces and al-Qaeda-allied groups that have emerged as leading rebel players.

Jaafari also reiterated Syria’s contention that existing U.N. guidelines place national sovereignty over any other factor in determining what passes across international borders. Throughout the war, the United Nations has said that government refusal to allow aid convoys not under its control to enter the country has hampered relief efforts.

But sponsors of the resolution, including the United States, France, Britain, Jordan, Australia and others, noted that Security Council actions, which are binding on U.N. members, trump all other measures.

The resolution also calls for renewed efforts to negotiate a political solution to the crisis. In ­statements, U.S. and other representatives traded blame with Jaafari on the failure of recent U.N.-sponsored peace talks in Geneva.