Speaking in Denmark, US secretary of state Hillary Clinton slammed the Russian government for continuing to support Syrian president Bashar Assad, even after last week's massacre of more than 100 people in the town of Houla.
She said Russia's position "is going to help contribute to a civil war" and rejected Russian officials' insistence that their stance actually is helping to ease the crisis.
On the first stop of a European tour, Mrs Clinton said Russia and China would have to be on board before the US and other nations might engage in what could become a protracted conflict in support of a disorganised rebel force.
Russia, along with China, has twice vetoed UN Security Council sanctions against Syria. Russia is Syria's closest ally other than isolated Iran, and Mrs Clinton said that without its support the international community is essentially frozen from taking concrete steps to end the violence.
"The Russians keep telling us they want to do everything they can to avoid a civil war because they believe that the violence would be catastrophic," Mrs Clinton said, noting that they are "vociferous in their claim that they are providing a stabilising influence". Read More