The United States and Russia clashed over Syria at the UN Monday after Secretary-General Ban Ki-moon urged the divided Security Council to speak with one voice and help the Mideast nation "pull back from the brink of a deeper catastrophe."

Washington and Moscow both called for an end to the bloody yearlong conflict -- but on different terms, leaving in doubt prospects of breaking a deadlock in the council over a new resolution.

U.S. Secretary of State Hillary Rodham Clinton rejected any equivalence between the "premeditated murders" carried by President Bashar Assad's "military machine" and the civilians under siege driven to self-defence.

Russia's Foreign Minister Sergey Lavrov said Syrian authorities "bear a huge share of responsibility" but insisted opposition fighters and extremists including al-Qaida are also committing violent and terrorist acts.

Lavrov said if the priority is to immediately end any violence and provide humanitarian aid to the Syrian people "then at this stage we should not talk about who was the first to start, but rather discuss realistic and feasible approaches which would allow (us) to achieve the cease-fire as a priority."

Clinton declared that the Security Council cannot "stand silent when governments massacre their own people, threatening regional peace and security in the process."

The ministerial debate in the council on challenges from last year's Arab Spring was dominated by the yearlong conflict in Syria, which has killed over 7,500 people, according to the United Nations.

Secretary-General Ban, who led off the debate, said the conflict has led the entire region into uncertainty and subjected citizens in several cities to disproportionate violence.

Russia, which is Syria's most powerful ally, and China have vetoed two U.S. and European-backed Security Council resolutions which would have condemned Assad's bloody crackdown, saying they were unbalanced and demanded that only the government stop attacks, not the opposition. Moscow accused Western powers of fueling the conflict by backing the rebels.

Earlier this month, the United States proposed a new draft which tried to take a more balanced approach, but diplomats said Russia and China rejected it.

Lavrov flew to New York from Cairo, where he had a tense meeting with Arab League foreign ministers. They have endorsed a plan for Assad to hand power to his vice-president, but the Russians are adamantly opposed to any resolution endorsing regime change.

In the end, the Arab League and Lavrov agreed on a plan that the Russia foreign minister said could lead to an early solution of the Syrian crisis: an immediate cease-fire, a clause preventing foreign intervention, assurances about humanitarian aid, an impartial monitoring mechanism and an endorsement of the mission by former UN chief Kofi Annan, the new U.N.-Arab League special envoy to Syria.

Annan left Syria on Sunday without a deal to end the conflict, while regime forces mounted a new assault on rebel strongholds in the north.

On Monday, Annan met Turkey's Prime Minister Recep Tayyip Erdogan in Ankara and told reporters the diplomatic process would take time.

"This a very complex situation," said Annan. "We are going to press ahead for humanitarian access, for the killings of civilians to stop, and that get everybody to the table to work out a political solution."

Clinton told reporters after meeting privately with Lavrov that she appreciated the opportunity to discuss the way forward and pointed out to him "my very strong view that the alternative to our unity on these points will be bloody internal conflict with dangerous consequences for the whole region."

She said everyone is waiting to hear Annan's advice on the best way forward, and the U.S. hopes that after Monday's council session and the recent meetings in Cairo and Damascus "we will be prepared in the Security Council to chart a way forward."

Lavrov said separate discussions with Clinton and the British and French foreign ministers "indicated that there is a growing understanding of the need not to talk to each other on the basis of take it or leave it, but to bring the positions together and to be guided not by the desire of revenge or punishment, who is to blame ... but by the interests of the Syrian people."

On the sidelines, the Quartet of Mideast peace mediators -- the UN, U.S., European Union and Russia -- met behind closed doors on the escalating Israeli-Palestinian conflict, which is witnessing the worst flare-up in violence in more than a year.

The ministerial meeting reviewed efforts to get the Palestinians and Israelis back to the negotiating table, but deep divisions remain and there is little hope of a breakthrough.