For decades, nuclear weapons have been largely peripheral to U.S.-China  relations, but the nuclear relationship is now growing more competitive  as both countries pursue major programs to modernize their forces.  China’s efforts to strengthen its relatively small nuclear arsenal seem  largely oriented toward improving survivability and do not appear to  constitute a shift away from the country’s long-standing No First Use  (NFU) policy. Nevertheless, the improvements are provoking anxiety in  Washington, which has long resisted acknowledging a state of mutual  nuclear vulnerability with China.  David Santoro is the President and CEO of The Pacific Forum and a  published author. His latest work, 'US-China Nuclear Relations: The  Importance Of Strategic Triangles', handles the sensitive matter of  regulation concerning nuclear weapons.