The six states -- China, Germany, France, Russia, the United Kingdom and the United States -- have for years offered Iran political and economic incentives in exchange for halting uranium enrichment, an effort that can produce both nuclear bomb material and fuel for civilian applications. Tehran has defended its atomic ambitions as strictly civilian in nature and steadfastly refused to consider shuttering its enrichment program.
Gates was reported to have said Washington would like the United Kingdom to maintain its nuclear arsenal, as he did not want the United States to have "sole responsibility" for ensuring extended nuclear deterrence to NATO members
U.S. President Barack Obama and Russian President Dmitry Medvedev in April signed the agreement. The deal requires the former Cold War adversaries to each cut their deployed strategic nuclear weapons to 1,550 warheads, down from the maximum of 2,200 allowed by 2012 under a 2002 agreement. They must both also restrict their active nuclear delivery vehicles to 700, with another 100 platforms allowed in reserve.
