A top U.S. arms control official on Monday sharply criticized Russia for suspending its participation in the last remaining nuclear weapons treaty, but said Washington will try to work with Moscow to continue its implementation. Russian President Vladimir Putin announced last week that the country would suspend participation in the New START treaty which obligated both Russia and the U.S. to commit to regular communications on the status of their nuclear arsenals, allow regular on-site inspections and abide by caps on the number of deployed and non-deployed warheads of each side.