SEOUL - North Korean nuclear weapons act as a deterrent to potential aggressors and as a foundation for its prosperity, the country's leader said in a speech delivered on Sunday and published in full by the country's KCNA news agency on Tuesday."Our nuclear strength is a reliable war deterrent and a guarantee to protect our sovereignty," Kim Jong-un said in a speech delivered to the central committee meeting of the ruling Workers Party of Korea.The speech appeared to emphasize a shift to economic development and accused the United States of seeking to drag North Korea into an arms race in a bid to create obstacles to economic improvement.