Hillary Clinton has claimed Russia's policy on Syria could lead to civil war in the country, as the United States' ambassador to the UN said the Assad regime's report on the Houla massacre was "a blatant lie".
The US Secretary of State bluntly criticised Russian backing of President Bashar al-Assad, during an address to students in Denmark.
Mrs Clinton said the Syrians were unlikely to listen to the US but added: "They will listen, maybe, to the Russians, so we have to keep pushing them".
She also criticised Russia's position on Syria, saying: "I have been telling them their policy is going to help to contribute to a civil war".
Mrs Clinton's claims came after it emerged that a Russian cargo ship carrying weapons had docked in Syria, a day after 108 people, including 34 children, were massacred in Houla.
The US Ambassador to the United Nations Susan Rice said the Russian shipment of arms to Syria was "reprehensible" but admitted it did not violate any laws.
Ms Rice said Russia's veto-wielding membership of the Security Council would not prevent possible future intervention in Syria. Some countries would consider bypassing Chinese and Russian opposition if violence worsened in the country, she said.
Our Middle East Correspondent John Ray, said that mass graves were still being dug in Houla, with villagers saying that the killers came from across the field.
The US ambassador to the UN also dismissed the Syrian Government's investigation into the massacre in Houla calling it "another blatant lie", adding that "there is no factual evidence ... that would substantiate that rendition of events".
The Prime Minister convened a meeting of the National Security Council today to discuss the growing possibility of all-out civil war in Syria.