The United States stepped up pressure on Russia to support a Syrian power transfer that would include President Bashar Assad's exit after the second reported massacre in weeks deepened doubts Kofi Annan's UN-backed peace plan can work.A senior US State Department official, Fred Hof, held talks on Friday with Russian Deputy Foreign Ministers Gennady Gatilov and Mikhail Bogdanov, the Foreign Ministry said. Hof made no comment to reporters outside the ministry building.Prospects for a political process appear increasingly slim, prompting Western states to redouble calls for Moscow to apply more pressure on Assad to end violence in which the United Nations says his forces have killed more than 10,000 people.On Thursday, UN Secretary-General Ban Ki-moon described the reported killing of at least 78 villagers by Assad's forces as "unspeakable barbarity" and warned civil war was imminent.International envoy Kofi Annan acknowledged his UN-Arab League peace plan, which Russia has strongly backed, was not working and said there must be "consequences" for those who do not comply.Russia, which helped win Assad's nominal support for the peace plan, says the reported massacre in Hama province and the killings of 108 people late last month in the Houla region underscore the need to support Annan's plan.Bogdanov said on Friday the six-point plan could be adjusted to improve implementation but its core elements must remain. The plan, which demands an end to the violence, calls for a political process but includes no direct call for Assad's exit.Russia has resisted pressure to change its stance on Syria and has not joined other nations in blaming the killings squarely on the government, saying both sides had a hand in the Houla massacre. It has not assigned blame for the latest killings but said they were aimed at scuttling Annan's plan.During a visit to Beijing by Putin, a regional security alliance led by Russia and China said it opposes military interference, forced power handovers and unilateral sanctions in dealings with the Middle East.Russian Foreign Minister Sergei Lavrov reiterated on Thursday that the UN Security Council - where Russia and China have twice used their vetoes to block condemnation of Assad's government - would not authorize foreign intervention in Syria."We continue to speak out decisively in support of Syria's sovereignty, and against foreign intervention in its affairs and attempts to force parameters of an internal Syrian solution upon it from outside," Bogdanov told state-run RIA news agency.But Moscow has criticized Assad at times and courted his opponents, suggesting it may be hedging its bets.Analysts say Putin could be lured by or seek an orchestrated exit by Assad that could be presented as the work of the people, particularly if he doubts Assad can hang onto power for long and sees a chance of Moscow maintaining influence.Russia could calculate that it has more to gain by claiming a peacemaking role than by backing Assad. But its influence has limits and any effort to engineer his exit would have to be carefully engineered to protect Russian interests and save face.US officials have suggested Secretary of State Hillary Clinton sent Hof to Moscow as part of an effort secure a transition strategy that the United States says must include Assad's full transfer of power.The Russian Foreign Ministry described the talks as "an exchange of opinions on ways to foster a peaceful resolution in Syria with an accent on mobilization of international support in the interests of fulfillment of Annan's plan by all sides".While the United States wants Russia to put pressure on Assad, Moscow says Western and Arab nations must use their influence to push insurgents fighting for the Syrian leader's downfall to halt violence and hold talks with the government.Eager to maintain its firmest Middle East foothold and stop Washington and the West from pushing governments from power, Russia has used its UN Security Council veto and other tools to protect Assad from coordinated condemnation and sanctions.President Vladimir Putin says he is not on Assad's side and Russia says it would be open to his exit from power as long as it is a result of an inclusive political process among Syrians without interference.