North Korea on Tuesday accused the United States of driving the global nuclear order into "the worst crisis" through its "nuclear proliferation activities" and used the accusation to defend its own nuclear program. The accusation came in a foreign ministry's "memorandum" carried by the Korean Central News Agency (KCNA), hours after Vice Foreign Minister Kim Son-gyong told the U.N. General Assembly in New York that North Korea's nuclear program is an "irresistible" force needed to protect its sovereignty and security against external threats. Washington has "irresponsibly abandoned its disarmament obligations as a nuclear-weapon state," the memorandum said. Its rapid buildup of nuclear forces and "blatant" nuclear proliferation, it said, left Pyongyang no choice but to "play a more active role" "as a responsible nuclear-weapon state." The document cast the U.S. as the main culprit behind global nuclear proliferation, citing its nuclear buildup and modernization and its withdrawal from arms-control treaties. North Korea also pointed to U.S. nuclear-powered submarine cooperation with Seoul a