SEOUL - Nuclear-armed North Korea unveiled a submarine-launched ballistic missile at a military parade in Pyongyang, state media reported Friday, in a show of strength days before Joe Biden's inauguration as US president.

The parade marked the once-every-five-years congress of the ruling Workers' Party, at which leader Kim Jong Un decried the US as his country's "foremost principal enemy".

"The world's most powerful weapon, submarine-launch ballistic missile, entered the square one after another, powerfully demonstrating the might of the revolutionary armed forces," the official KCNA news agency said.

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Kim oversaw the display, which included rockets with a "powerful striking capability for thoroughly annihilating enemies in a preemptive way outside the territory", it said.

The phrasing implies the weapons have a range that extends beyond the Korean peninsula and could at least reach Japan.

The US stations 28,500 troops in South Korea to defend it against its neighbor, and also has a significant military presence in Japan.

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Analysts say the North is using the congress to send Washington's incoming administration a message of strength in an attempt to extract concessions.

Kim and Donald Trump had a tumultuous relationship, engaging in mutual insults and threats of war before an extraordinary diplomatic bromance featuring headline-grabbing summits and declarations of love by the outgoing US president.

But little substantive progress was made, with the process deadlocked after their February 2019 meeting in Hanoi broke down over sanctions relief and what Pyongyang would be willing to give up in return.

The North is under multiple sets of international sanctions over its banned nuclear weapons and ballistic missile programs.

At the same time it is under a self-imposed coronavirus blockade, having closed its borders last January to protect against the virus that first emerged in neighboring China, adding to the pressure on its moribund economy.

The change of leadership in Washington presents a challenge for Pyongyang: Biden is associated with the Obama administration's "strategic patience" approach and characterized Kim as a "thug" during the presidential debates.

The US is expected to return to more orthodox diplomatic approaches under Biden, such as insisting on extensive progress at working-level talks before any leaders' summit can be considered.

NUCLEAR SUBMARINE

Pyongyang has poured vast resources into its weapons programs, which have made rapid progress under Kim and which it says it needs to defend itself against a possible US invasion.

"The majestic elite units and invincible iron-clad ranks of the Republic which will proudly pass Kim Il Sung Square represent our absolute power," North Korean defence minister Kim Jong Gwan said in a speech ahead of the Thursday evening parade, KCNA reported.

The display also included infantry troops, artillery, tanks, and a flypast with aircraft forming the number "8" to commemorate the congress, it said.

But the North is carefully calibrating its messaging and the KCNA description did not mention any intercontinental ballistic missiles (ICBMs), suggesting that the parade was on a smaller scale than the North's previous such display in October.

At that time it showed off a huge new ICBM on an 11-axle vehicle that analysts said was the largest road-mobile, liquid-fueled missile in the world.

At the congress, Kim said the North had completed plans for a nuclear-powered submarine -- something that would change the strategic balance if it was built and went into service.

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