Russian president Dmitry Medvedev has told the UN and Arab League envoy to Syria that his mission “may be the last chance for Syria to avoid a protracted bloody civil war”.
Mr Medvedev also told Kofi Annan that he has Russia's full support.
Mr Annan was in Moscow today for meetings with Russia's president and foreign minister.
He now travels to China, which with Russia has shielded Syrian leader Bashar Assad from United Nation sanctions.
Syria is Moscow's last remaining ally in the Middle East and is a major customer for Russia's arms industry, but Russia has recently shown impatience with Dr Assad.
Up to 8,000 have died in the year-long uprising against Dr Assad's regime.
Meeting in Korea, US president Barack Obama and Turkish prime minister Tayyip Erdogan discussed how to support the opposition with non-lethal aid.
Western and Arab states want Dr Assad to stand down but Russia, Syria's long-time ally, says the armed rebels must also cease fire and withdraw their forces.
In a statement ahead of the meeting, the Kremlin said it would be hard to enforce a halt to the violence "until external armed and political support of the opposition is terminated".
Mr Annan has drawn up a six-point peace plan, including demands for a ceasefire, the immediate withdrawal of heavy armour from residential areas and access for humanitarian assistance.
But, more than a year after the start of the uprising, the prospect of a negotiated peace seemed more remote than ever, with clashes reported around the country.
Moscow has accused the West of being too one-sided, arguing that outside support for rebels is fuelling the fighting in Syria, which hosts a Russian naval base.
But Russia and China, which have vetoed two UN resolutions critical of Damascus, did support a Security Council statement this week endorsing Annan's mission. The former UN chief is due to fly to China after Russia talks.
In the korean capital Seoul, Mr Obama and Mr Erdogan discussed providing medical supplies and communications support to the Syrian opposition but there was no talk of providing lethal aid for rebel forces.
White House deputy national security adviser Ben Rhodes, speaking to reporters after the two leaders met on the eve of a nuclear security summit, said Washington and Ankara were open to considering further "non-lethal" aid for the Syrian opposition at a "Friends of Syria" meeting in Turkey on April 1st.
"We worked on a common agenda in terms of how we can support both humanitarian efforts ... (and) the efforts of Kofi Annan to bring about much needed change (in Syria)," Mr Obama said after his meeting with Mr Erdogan, a sharp critic of Dr Assad.
New York-based Human Rights Watch, in a report today, quoted residents from Syria's northwestern province of Idlib saying Assad loyalists had forced them to march in front of advancing army offensives this month to retake control of areas that had fallen into the hands of the opposition.
"Syrian government forces have endangered local residents by forcing them to march in front of the army during recent arrest operations, troop movements, and attacks on towns and villages in northern Syria," it said.
HRW published videos, obtained from opposition activists, in which people in civilian clothes walk in front of several armed soldiers and infantry fighting vehicles.
Activists say the army had compelled the men to walk in front to protect the soldiers. The statement said that residents reported government forces placing children on tanks and inside security buses.
"The Syrian army's use of human shields is yet another reason why the UN Security Council should refer Syria to the International Criminal Court" said Ole Solvang, a HRW emergencies researcher.
It was impossible to verify reports independently because Syrian authorities have prevented foreign journalists and human rights workers from entering affected areas.
Reuters