North Korea’s first ruling party congress for nearly 40 years formally adopted leader Kim Jong-Un’s policy of developing the country’s nuclear arsenal in tandem with the economy, AFP reports.

The thousands of delegates to what is technically North Korea’s top decision-making body adopted a decision to simultaneously push forward economic construction and “boost self-defensive nuclear force both in quality and quantity.”

It also enshrined a policy of not using nuclear weapons unless its sovereignty is threatened by another nuclear power, and of working towards the eventual reunification of the divided Korean peninsula.

“But if the south Korean authorities opt for a war… we will turn out in the just war to mercilessly wipe out the anti-reunification forces,” said the document published by the North’s official KCNA news agency.

Reiterating the North’s argument that its push for a nuclear deterrent was forced on it by American hostility, the congress said the nuclear weapons program would move forward “as long as the imperialists persist in their nuclear threat.”

In a speech before the congress on Saturday, Kim adopted a soft tone on his country’s nuclear program, saying the country would only use nuclear weapons if attacked by a nuclear power, adding he wanted improved relations with previously “hostile” nations.

Kim had opened the congress with a defiant defense of his country’s nuclear weapons program, praising the “magnificent… and thrilling” test of what Pyongyang claimed was a powerful hydrogen bomb on January 6.

North Korea last month held a successful submarine nuclear missile launch that is said to bring the United States within range. Despite the successful tests, however, the rogue state has also embarrassingly failed two missile tests in recent weeks.