North Korea said on Tuesday its main nuclear complex was operating and it was working to improve the "quality and quantity" of its weapons which it could use against the United States at "any time." The comments follow a declaration by the North in 2013 vowing to restart all nuclear facilities, including the main nuclear reactor in Yongbyon that had been shuttered. "If the U.S. and other hostile forces persistently seek their reckless hostile policy towards the DPRK and behave mischievously, the DPRK is fully ready to cope with them with nuclear weapons any time," the director was quoted as saying.