SEOUL--North Korea on Sunday fired what appeared to be the most powerful missile it has tested since U.S. President Joe Biden took office, as it revives its old playbook in brinkmanship to wrest concessions from Washington and neighbors amid a prolonged stalemate in diplomacy.

Japanese officials said the missile, based on their initial assessment of its flight path, potentially reached a maximum altitude of 2,000 kilometers and traveled 800 kilometers before landing in the sea.

The flight details suggest the North tested its longest-range ballistic missile since 2017, when it flight-tested three intercontinental range ballistic missiles that demonstrated the potential range to reach deep into the American homeland.

Sunday’s test was the North’s seventh round of weapons launches this month. The unusually fast pace of tests indicate an intent to pressure the Biden administration over long-stalled nuclear negotiations.

The launch came after North Korean leader Kim Jong Un chaired a ruling party meeting on Jan. 20 where senior party members made a veiled threat to resume testing of nuclear explosives and ICBMs, which Kim suspended in 2018 while initiating diplomacy with the United States.

Japanese Chief Cabinet Secretary Hirokazu Matsuno said the missile flew for around 30 minutes and landed in waters outside Japan’s exclusive economic zone.

South Korea’s Joint Chiefs of Staff said the North launched one suspected ballistic missile from a northern inland area but didn’t immediately provide further flight details.

The Japanese assessments suggest that the North tested an intermediate-range ballistic missile or possibly even a weapon approaching ICBM capacities, said Lee Choon Geun, a missile expert and honorary research fellow at South Korea’s Science and Technology Policy Institute.

“I think this means that the North’s moratorium (on long-range testing) is effectively over,” Lee said.

Japan’s coast guard issued a maritime safety warning, saying that an object that was potentially a North Korean ballistic missile could have already landed, but there were no immediate reports of damage to boats or aircraft.

The launch came three days after North Korea fired two short-range ballistic missiles into the sea on Thursday. The North also flight-tested a pair of purported long-range cruise missiles on Tuesday while vowing to strengthen its nuclear “war deterrent” and build more powerful weapons.

North Korea has been ramping up its testing activity in recent months, including seven rounds of weapons launches so far in 2022, demonstrating its military might amid pandemic-related difficulties and a prolonged freeze in nuclear diplomacy with the United States.

Experts say the North could halt its testing spree after the start of the Beijing Winter Olympics next week out of respect for China, its major ally and economic lifeline. But there’s also expectation that the North could significantly up the ante in weapons demonstrations once the Olympics end in February to grab the attention of the Biden administration, which has been focusing more on confronting China and also Russia over its conflict with Ukraine.

“North Korea is launching a frenzy of missiles before the start of the Beijing Olympics, mostly as military modernization efforts. Pyongyang also wants to boost national pride as it gears up to celebrate political anniversaries in the context of economic struggles,” said Leif-Eric Easley, a professor at Ewha University in Seoul.

“It wants to remind Washington and Seoul that trying to topple it would be too costly. By threatening stability in Asia while global resources are stretched thin elsewhere, Pyongyang is demanding the world compensate it to act like a ‘responsible nuclear power,’” Easley added.

North Korea has justified its testing activity as an exercise of its rights to self-defense and threatened stronger action after the Biden administration imposed fresh sanctions following two tests of a purported hypersonic missile earlier this month.

Kim has repeatedly vowed to bolster his nuclear forces since his summitry with then-President Donald Trump derailed in 2019 with the Americans rejecting North Korea’s demands for major sanctions relief in exchange for a partial surrender of its nuclear capabilities.

While desperate for outside relief as his economy decays under crippling U.S.-led sanctions and pandemic-related difficulties, Kim has showed no willingness to surrender the nuclear weapons and missiles he sees as his strongest guarantee of survival. Analysts say Kim’s pressure campaign is aimed at forcing Washington to accept the North as a nuclear power and convert the latter’s nuclear disarmament-for-aid diplomacy into negotiations for mutual arms reduction.

Kim last year announced a new five-year plan for developing weapons and issued an ambitious wish list that included hypersonic weapons, spy satellites, solid-fuel intercontinental ballistic missiles and submarine-launched nuclear missiles.

State media said Friday that Kim visited an unspecified munitions factory producing a “major weapons system,” and that the workers pledged loyalty to their leader who “smashes with his bold pluck the challenges of U.S. imperialists and their vassal forces.”