Kim Jong-un pledges to expand North Korea's nuclear arsenal

North Korean leader Kim Jong-un said US policy towards his country would "never change"

North Korean leader Kim Jong-un has said the US is his country's "biggest enemy" and that he does not expect Washington to change its policy toward Pyongyang - whoever is president.

Addressing a rare congress of his ruling Workers' Party, Mr Kim also pledged to expand North Korea's nuclear weapons arsenal and military potential.

He said that plans for a nuclear submarine were almost complete.

His comments come as US President-elect Joe Biden prepares to take office.

Analysts suggest Mr Kim's remarks are an effort to apply pressure on the incoming government, with Mr Biden set to be sworn in on 20 January.

Mr Kim enjoyed a warm rapport with outgoing US President Donald Trump, even if little concrete progress was made on negotiations over North Korea's nuclear programme.

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In his latest address to the Workers' Party - only the eighth congress in its history - Mr Kim said Pyongyang did not intend to use its nuclear weapons unless "hostile forces" were planning to use them against North Korea first.

He said the US was his country's "biggest obstacle for our revolution and our biggest enemy... no matter who is in power, the true nature of its policy against North Korea will never change," state news agency KCNA reported.

His speech outlined a list of desired weapons including long-range ballistic missiles capable of being launched from land or sea and "super-large warheads".

North Korea has managed to significantly advance its arsenal despite being subject to strict economic sanctions.

Earlier this week, Mr Kim admitted that his five-year economic plan for the isolated country failed to meet its targets in "almost every sector".

North Korea closed its borders last January to prevent Covid from entering the country.

Its authorities say the country has not had a single Covid case since the pandemic began but experts say this is highly unlikely due to North Korea's cross-border trade with China.

Trade with China has plummeted by about 80%. Typhoons and floods have devastated homes and crops in North Korea, which remains under strict international sanctions, including over its nuclear programme.

The speech is likely to be Mr Kim's way of setting the stage for talks with President-elect Joe Biden who will take office in less than two weeks' time.

The aim is perhaps to put pressure on Washington to show that Pyongyang has no intention of being cowed by sanctions and will continue to expand its nuclear arsenal.

Mr Kim had three summits with Donald Trump - but they failed to reach a deal. However, North Korea is in a difficult and bleak economic position caused by strict sanctions, border blockades to prevent the spread of Covid-19 and devastating floods.

This message may seem threatening, but some analysts believe that there is still room for diplomacy.