Nuclear-armed North Korea's leader Kim Jong Un vowed to strengthen its military capabilities at a key ruling party meeting, state media reported Thursday, just weeks before Joe Biden's inauguration as US president.

In his work report to the Workers' Party congress Kim pledged to place "the state defence capabilities on a much higher level, and put forth goals for realising it", the official Korean Central News Agency reported.

Outgoing US President Donald Trump had an extraordinary diplomatic bromance with Kim, but talks between Washington and Pyongyang have been stalled since the two men's second summit in Hanoi broke down in February 2019 over sanctions relief and what Pyongyang would be willing to give up in return.

Analysts say the North will look to use the five-yearly congress to send the incoming administration a message, but will tread carefully with Biden having characterised Kim as a "thug" during the presidential debates, while Pyongyang has called him a "rabid dog".

A man watches a television screen showing news footage of North Korean leader Kim Jong Un attending the 8th congress of the ruling Workers' Party held in Pyongyang, at a railway station in Seoul on January 6, 2021
A man watches a television screen showing news footage of North Korean leader Kim Jong Un attending the 8th congress of the ruling Workers' Party held in Pyongyang, at a railway station in Seoul on January 6, 2021 AFP / Jung Yeon-je

KCNA did not refer to nuclear weapons in its report or give specific details of Kim's goals.

But at a military parade in October Pyongyang showed off a huge new missile that analysts concurred was the largest road-mobile, liquid-fuelled missile anywhere in the world, and was highly likely to be designed to carry multiple warheads in independent re-entry vehicles (MIRVs).

North Korea says it needs nuclear weapons to defend itself against a possible US invasion, and for decades has poured vast amounts of resources into developing them.

Its progress accelerated rapidly under Kim, including by far its most powerful nuclear test and missiles capable of reaching the whole of the US.

The isolated, impoverished North is subject to multiple international sanctions as a result.