By Daphne Psaledakis, Simon Lewis and Matt Spetalnick WASHINGTON (Reuters) -The United States on Thursday imposed sanctions on Russia in retaliation for its invasion of Ukraine, targeting its two biggest banks and members of the elite in new measures as Washington warned more action could come. Among the targets were five major Russian banks, including state-backed Sberbank and VTB, the country’s two largest lenders, as well as wealthy individuals and their families. The United States also announced new export control measures. Washington imposed the new sanctions after Russian forces invaded …