The United States imposed its toughest sanctions yet on Moscow on Wednesday, and Russian stocks and the ruble tumbled on Thursday. “From the West’s perspective they could not have chosen a better time to intensify sanctions,” said Societe Generale strategist Regis Chatellier. “Until a few weeks back Russia was in a position of relative strength because there was massive pressure on oil but that is not the case any more.” The new U.S. sanctions effectively shut off medium and longer-term dollar funding for companies close to Vladimir Putin.