The United States and its European and Arab partners have agreed to drop a demand to impose U.N. sanctions and a voluntary arms embargo on Syria, in exchange for a commitment from Russia to allow adoption of a U.N. Security Council resolution that paves the way for President Bashar al-Assad’s departure from power.

The latest offer — outlined in a new version of a draft resolution under negotiations in the 15-nation council — represents a retreat by the United States and its European and Arab allies, stripping away the most painful measures aimed at Syria, and taking off the table the issue of its weapons purchases from Russia, Syria’s closest ally.

But the pact would for the first time place the Security Council, and possibly Russia, squarely behind an Arab League plan outlining a timetable for a transfer of power to a government of national unity, and ultimately new parliamentary and presidential elections. And it would mark the first time since the violence began that the council has adopted a binding resolution condemning Syria’s conduct.

Security Council diplomats said they are confident that they have fashioned the broad parameters of a possible deal that would end months of inaction on Syria by the council. But they cautioned that Russia has yet to agree to support an unambiguous endorsement of the Arab League political plan, and that the entire proposal could unravel if it doesn’t.

Western and Arab sponsors planned to continue pressing their case for a resolution on Thursday night. Russia’s U.N. ambassador, Vitaly Churkin, threatened to veto the measure if it was brought to a vote Friday, saying his government needed more time to negotiate the terms of the resolution, said two council diplomats who were in a closed-door session.

The Arab League secretary general, Nabil Elaraby, and the chairman of the league’s council of ministers, Qatari Prime Minister Hamad bin Jasim al-Thani, have appealed to the Security Council to lend its weight to a plan calling for the beginning of talks between the Syrian government and opposition, leading to the establishment of a unity government within two months. Under the plan, Assad would be required to grant one of his deputies authority to cooperate with the united government, which would be led by an individual selected by rival parties.

Elaraby sought to reassure Russia that the resolution is not intended to justify military action, to sanction Syria or to force Assad to leave power.

The Russians “don’t want the Arab peace plan, which says the president delegates power to the vice president,” he said in an interview with CNN. “We didn’t ask that the president should step down, but only to delegate powers to the vice president.”

But Elaraby said that Russian support for even a new, watered-down resolution would “put pressure” on the regime and drive home that Moscow won’t stand up for it indefinitely.

Russia, which is backed by China, has insisted that the Arab League and the Security Council lack the right to impose a “pre-cooked” political settlement on Syria, saying any plan for a transition needs to be negotiated by the Syrian government and the opposition. Churkin has insisted that his government would block any resolution that was designed to bring about regime change in Syria. It has offered to host talks in Moscow.

In an effort to assuage Russian concerns that the draft might serve as part of a pretext for future military action, the sponsors of the text have offered to include language expressly stating that the resolution does not “compel states to resort to the use of force or the threat of force.”

The latest draft replaces that language with a provision, which is still not agreed upon by all parties, that expresses the council’s intention “to resolve the political crisis in Syria peacefully without foreign military intervention.”

The Syrian government launched a brutal campaign of repression against peaceful demonstrators early last year, killing between 5,000 and 6,000 people, according to U.N. and other diplomatic estimates. In recent months, the violence has worsened as opposition forces have taken up arms against the Assad government, leading the country to the brink of all-out civil war.

The Security Council adopted a presidential statement in August condemning the Syrian government’s conduct and calling for a political dialogue with the opposition.

In October, however, Russia and China vetoed a draft resolution that threatened sanctions against Damascus if it didn’t halt the killing.

The latest draft “condemns the continued widespread and gross violations of human rights and fundamental freedoms by the Syrian authorities” and demands that Syria immediately cease attacks against protesters. It also condemns violent attacks against government targets by armed opposition forces.

But the text struck out a provision calling on states to “take necessary steps” to prevent the flow of weapons into Syria. It also eliminated another provision that called on states to reinforce existing Arab League financial and travel sanctions, and to impose similar measures against Syria.

If Syria fails to comply with the U.N. demands, according to the draft, the Security Council, in consultation with the Arab League, will consider “further measures,” including possible sanctions, to ensure Damascus does comply.