Pyongyang has long insisted on its right to a nuclear weapon and ballistic missile programmes although they are forbidden under the terms of UN Security Council sanctions. It enshrined its nuclear status in its constitution in 2023.

"Our status as a nuclear power is absolutely non-negotiable," Kim's sister Kim Yo Jong said in a statement published by North Korea's official Rodong Sinmun, adding that the North "will not tolerate any threats".

The statement by Kim Yo Jong, a key player in the country's communications and foreign policy, came on the eve of Xi's visit to North Korea from Monday to Tuesday, according to state media.

Beijing is a vital source of political and economic support to North Korea, which is one of the most diplomatically isolated countries in the world and under heavy international sanctions.

Xi's upcoming visit to Pyongyang would be his first in seven years, and comes after he hosted back-to-back summits with US President Donald Trump and Russia's Vladimir Putin last month.

Pyongyang has repeatedly declared itself an "irreversible" nuclear state since Kim Jong Un's 2019 summit with Trump collapsed over the scope of denuclearisation and sanctions relief.

North Korea's leader has since been emboldened by the war in Ukraine, securing critical support from Moscow after sending thousands of troops to fight alongside Russian forces.

-False information-

Kim Yo Jong, in her statement, went on to slam Washington over its comments that the goal of North Korea's denuclearisation had been reaffirmed during last month's summit between Donald Trump and Xi Jinping in Beijing.

The White House posted a fact sheet following the summit stating that "President Trump and President Xi confirmed their shared goal to denuclearize North Korea", which Kim Yo Jong said was false.

"Some officials in the United States still have yet to awaken from their escapist and anachronistic dream," she said.

"This is nothing more than Washington's habitual dissemination of false information."

She rejected Washington's attempts to deny or challenge the North's status as a nuclear power, saying it "carries no legal force".

"The policy of continuously strengthening the country's self-defensive nuclear deterrent, as set out by the nation's leader, is an irreversible course that must be implemented without fail," she added.