John Bacon, and Steph Solis

USA TODAY

North Korea will not deploy nuclear weapons unless the communist nation's enemies use them first and will attempt to normalize relations with "hostile" countries, leader Kim Jong Un revealed Sunday.

Kim warned the U.S. to stay out of Korean affairs but offered to enter talks with South Korea aimed at easing tensions on the peninsula. "As a responsible nuclear weapons state, our republic will not use a nuclear weapon unless its sovereignty is encroached upon by any aggressive hostile forces with nukes," Kim told the Workers' Party of Korea congress in Pyongyang. Kim added that the North "will faithfully fulfill its obligation for non-proliferation and strive for the global denuclearization."

Kim opened the first formal gathering of his party in more than three decades on Friday by celebrating the "great success" of his nuclear weapons program. The congress is viewed as Kim's formal coronation as leader of the nation of 25 million people, most of whom live in poverty.

The congress has also served as a launch vehicle for his five-year plan to improve the battered economy by emphasizing increased agricultural and manufacturing production and involvement in the global economy.

After decades of emphasizing military strength under his father, Korea is moving toward Kim's “byongjin” — a two-pronged approach aimed at enhancing nuclear might while improving living conditions. Kim said he wants to expand the country's electricity resources using nuclear power plants, although the North currently does not have nuclear power plants.

"They went from guns and steel to nukes and butter," James Person, who coordinates the Center for Korean History and Public Policy at the Washington-based Wilson Center, recently told USA TODAY. "They have the nukes, we can hope they decide to start concentrating on the butter."

Kim's pledge of restraint comes at a time when the North continues to conduct nuclear weapon tests. In January, North Korea carried out its fourth nuclear test in a decade. When a rocket launch in February drew worldwide criticism as a missile test violation, intensified U.N. sanctions quickly followed.

Those sanctions continue to hamstring Pyongyang's economic efforts.

Kim repeatedly claimed triumph over the U.S., crediting the "heroic struggle"of Koreans and his political party for "victory after victory in the protracted fierce confrontation with the imperialists and the U.S." But he pledged to "improve and normalize the relations with those countries which respect the sovereignty of (North Korea) and are friendly towards it, though they had been hostile toward it in the past."

Still, Kim said the North had no plans to discard its policy of developing nuclear weapons.

Two weeks ago, South Korean President Park Geun Hye said North Korea had completed preparations for a fifth nuclear test, and the Institute for Science and International Security issued a similar warning.

The North’s Korean Central Television showed Kim's speech Sunday, although it probably was delivered the previous day, the Associated Press reported. North Korean news outlets including the state-run Korean Central News Agency (KCNA) published excerpts from the speech before his party congress. The gathering is the first since 1980 and the first for Kim, who assumed power in 2011 following the death of his father Kim Jong Il.

Kim spoke of reunification with the South, but South Korean officials remain wary of Kim's intentions to remain a nuclear state, the South's Yonhap news agency reported.

North Korea is among the world's most repressive and reclusive states and worst violators of human rights, according to the U.S. State Department and Human Rights Watch. Its citizens are denied the freedoms of speech, press, assembly, association, religion, movement and worker rights, according to the State Department.

Defectors report wanton killings, disappearances, arbitrary detention, torture and systematic forced labor, according to State Department's Country Reports on Human Rights Practices for 2015, which was released in April.

Contributing: Oren Dorell