Peace envoy Kofi Annan said on Friday he was "frustrated and impatient" a week after a massacre in Syria of 108 people shocked the world, and there were signs Russia might be moving closer to the West's position on tackling the crisis.
President Vladimir Putin denied that Russia, which has a base in Syria and supplies it with weapons, was providing the government with the means to crush rebels, brushing off U.S. comments that its latest shipment to Syria was "reprehensible".
Putin, speaking after talks with German Chancellor Angela Merkel and before a meeting with French President Francois Holland, restated that Moscow does not back any side in Syria and said patience was needed to achieve a political solution.
World powers increasingly fear that Syria, where more than 10,000 people have been killed in a 15-month uprising against President Bashar al-Assad, will slide into an all-out civil war that could also trigger regional conflict.
"I think perhaps I am more frustrated than most of you because I am in the thick of this," Annan told reporters after talks in Beirut with Lebanese Prime Minister Najib Mikati. "I want to see things move faster."
Syrian rebels, who agreed to Annan's April 12 truce plan, have urged him to declare the plan dead, freeing them from a commitment that both sides have repeatedly violated.
Damascus says it wants Annan's plan to succeed in ending the violence so the crisis can be resolved through political talks.
Although refusing to declare the ceasefire a failure, Annan welcomed any further steps from the U.N. Security Council.
"If there are other options on the table, I will say 'bravo' and support them," he said.
OUTRAGE OVER HOULA
Outrage at last Friday's mass killings in Houla, documented by U.N. observers, prompted a host of Western countries to expel Syria's senior diplomats, and to press Russia and China to allow tougher action by the U.N. Security Council.
U.N. Secretary General Ban Ki-moon said in Istanbul that the 300 observers were not in Syria "to passively bear witness to the slaughter of innocent citizens".
"We are there to help bring about the ceasefire. We are there to record violations of human rights and also violations of the Annan peace plan," he said.
China and Russia back Annan's plan, the only broadly accepted initiative to halt the bloodletting in Syria, and reject any intervention or U.N.-backed sanctions.
The 193-nation U.N. General Assembly is planning to meet next week to discuss the crisis in Syria and the massacre in Houla. Annan and U.N. human rights chief Navi Pillay are likely to address the assembly on Thursday, U.N. diplomats said.
Annan will also speak to the 15-nation U.N. Security Council that day about the lack of progress implementing his peace plan.
It was not clear if the assembly planned to pass a resolution or declaration. Its decisions are not legally binding but its inclusiveness means it could send a strong signal.
Merkel and Hollande were expected to try to persuade Putin that the West is not challenging Russian strategic interests.
The West is averse to military intervention, though Hollande said that could change if the U.N. Security Council backed it - only possible if Russia and China do not veto it.
U.S. Ambassador to the U.N. Human Rights Council Eileen Chamberlain Donahoe said her hope was that Russia was "on the cusp of joining with us to use the leverage we have together to make sure that this conflict does not spiral out of control".
In negotiations over the text of a U.N. resolution on the Houla massacre, she said the Russians were "very interested, more than ever in the past, to come to an agreement".
However, Russia on Friday backed the Syrian government's assertion that the massacre was the work of anti-government forces intent on undermining peace efforts.
The U.N. peacekeeping chief has said it was probably carried out by the Syrian army and pro-Assad "shabbiha" militiamen.
Moscow said the killings were the result of "financial aid and contraband supplies of modern weapons to militants".
Donahoe said U.S. Secretary of State Hillary Clinton would meet Russian Foreign Minister Sergei Lavrov this weekend.
Clinton, speaking in Oslo, said Russia was seen in Damascus and at the United Nations as supporting the continuity of Assad's rule. But she said Washington was prepared to cooperate if Moscow was ready to work on a political transition in Syria.
Putin told reporters in Berlin: "We have a good, long-standing relationship with Syria, but we do not support any side from which the threat of a civil war may emerge ...
"I agree with Madame Chancellor (Merkel) that our common task is to prevent the situation from developing under such an unfavorable scenario. Today we are seeing the signs of an emerging civil war. It is extremely dangerous," he added.
"As for supplying weapons, Russia does not provide weapons that could be used in a civil conflict."
The Kremlin does not want to lose its firmest foothold in the Middle East - a client for billions of dollars' worth of weapons and the host of Russia's only warm-water naval port outside the former Soviet Union.
GUNFIRE AND CLASHES
The Syrian Observatory for Human Rights, a British-based monitoring group, said at least 20 people were killed in clashes in Syria on Friday. It said hundreds of thousands of civilians had attended opposition protests around the country.
A day before, a dozen workers were killed near the western town of al-Qusair when gunmen loyal to Assad ordered them off a bus and shot them, activists said. Syrian media blamed "terrorists".
Video released by activists showed the corpses of 12 men, two of them with the tops of their heads shot away, laid out on the ground near the town of al-Qusair, which like Houla is about 20 km from the city of Homs, a hotbed of opposition to Assad.
Hamza Al-Buweida, a local opposition activist, said a survivor had told him the dead men had been returning from work at a fertilizer company in al-Buweida al-Sharqiya.
"They stopped, as usual, at a Syrian army checkpoint. But about 300 meters after the checkpoint a yellow car with four armed shabbiha (pro-Assad militia) stopped their car," he told Reuters over Skype.
"They took money off the men and then killed them one by one with gunshots to the head. More than 300 bullets were found in the bodies," he said.
It was impossible to verify Buweida's account. Syria has restricted journalists' access since the start of the uprising against Assad 15 months ago.
Activists say 50 to 100 people have died daily this week, including civilians, soldiers and anti-Assad rebels.
Syrian forces and pro-government militia accused of committing a massacre in Houla could face prosecution for crimes against humanity, the United Nations said on Friday.