RUSSIA accused the United States of carrying out preparations at its nuclear test site in Nevada but said that Moscow would not restart its own nuclear testing programme unless Washington did. Deputy Foreign Minister Sergei Ryabkov made the charge as Russia's lower house of parliament urgently studies how to revoke Moscow's ratification of a landmark treaty banning nuclear tests and as tensions with the West are at their highest level since the 1962 Cuban missile crisis. A U.S. State Department spokesperson rejected Ryabkov's allegation, calling it "a disturbing effort by Moscow to heighten nuclear risks and raise tensions in the context of…