FILE - In this Sept. 5, 2013 file photo, President Barack Obama shakes hands with Russian President Vladimir Putin during arrivals for the G-20 summit at the Konstantin Palace in St. Petersburg, Russia, Thursday, Sept. 5, 2013. Congress is stepping up pressure on the White House to confront Russia over allegations that it is cheating on a key nuclear arms treaty, a faceoff that could further strain U.S.-Moscow relations and dampen President Barack Obama's hopes to add deeper cuts in nuclear arsenals to his legacy. (AP Photo/Pablo Martinez Monsivais)