By Mark Trevelyan LONDON (Reuters) – Russia said on Sunday that it was counting on China to help it withstand the blow to its economy from Western sanctions over the war in Ukraine, but the United States warned Beijing not to provide that lifeline. Russian Finance Minister Anton Siluanov said sanctions had deprived Moscow of access to $300 billion of its $640 billion in gold and foreign exchange reserves, and added that there was pressure on Beijing to shut off more. “We have part of our gold and foreign exchange reserves in the Chinese currency, in yuan. And we see what pressure is being exer…