North Korea has unveiled for the first time what it says is a nuclear-powered submarine under construction, a weapons system that can pose a major security threat to South Korea and the US.

The comments have sparked fears the US might favour talks on nuclear arms reduction with North Korea instead of full denuclearisation.

North Korea has conducted a slew of underwater-launched ballistic missile tests since 2016, but all launches were made from the same 2,000-tonne-class submarine which has a single launch tube. Many experts call it a test platform, rather than an operational submarine in active service.

U.S. President Donald Trump said on Thursday he still has a good relationship with North Korean leader Kim Jong Un, with whom he held several summits during his first term, and referred to North Korea once again as a "nuclear power.

U.S. President Donald Trump reaffirmed his relationship with North Korean leader Kim Jong Un, referring to North Korea as a nuclear power. During an Oval Office meeting with NATO Secretary-General Mark Rutte,

US President Donald Trump stated that he still maintains good relations with North Korean leader Kim Jong Un, with whom he held several summits during his first term. The White House leader once again referred to North Korea as a "nuclear state,

U.S. President Donald Trump on Thursday expressed his desire to reestablish the relationship that he had with North Korean leader Kim Jong-un during his first term, boasting that he "got along great" with the reclusive leader.

U.S. President Donald Trump claimed Thursday to have a "great" relationship with North Korean leader Kim Jong-un, and described the recalcitrant country as a "nuclear power," as he has voiced openness to reengaging with the dynastic ruler.