North Korea's leader says his country would only use nuclear weapons first if its sovereignty is violated.
Kim Jong Un also said on May 8 that he is ready to improve relations with "hostile" countries. He called for talks with South Korea and for the United States not to interfere with relations between the two countries.
Kim was speaking in Pyongyang at the first Workers' Party congress to be held in decades.
North Korea has been under intense diplomatic pressure following a recent nuclear test and a long-range missile test.