President Joe Biden warned North Korea on Thursday that the United States "will respond accordingly" if it intensifies its military tests, after Pyongyang fired two missiles in its first major provocation since taking office.

The nuclear-armed North has a long history of using weapons tests to increase tensions, in a process carefully calibrated to try to advance its objectives.

Biden's response demonstrates a change of tone from his predecessor Donald Trump, who struck up an extraordinary diplomatic bromance with North Korean leader Kim Jong Un and last year repeatedly downplayed similar short-range launches.

U.S. President Joe Biden takes questions as he holds his first formal news conference in the East Room of the White House in Washington, U.S., March 25, 2021.

Pyongyang had been biding its time since the new administration took office, without even officially acknowledging its existence until last week.

But on Thursday it launched two weapons from its east coast into the Sea of Japan, known as the East Sea in Korea.

It was a violation of UN resolutions and the United States was "consulting with our partners and allies," Biden said, warning North Korea that "there will be answers if they decide to escalate. We will respond accordingly."

North Korea launched two weapons from its east coast on Thursday

I am also prepared for some form of diplomacy, but it has to be conditional on the end result of denuclearization, "he told reporters.

- 'Nuclear capacity' -

Washington and Tokyo said North Korea had fired ballistic missiles, the development of which is prohibited under UN Security Council resolutions that have imposed multiple sanctions on the isolated country.

Pyongyang insisted on Friday that the test involved a "guided tactical projectile" with a solid fuel engine, and its official KCNA news agency said it was overseen by senior official Ri Pyong Chol, rather than leader Kim Jong Un.

The weapons hit a target 600 kilometers (370 miles) away, KCNA said, beyond the 450 kilometers reported by the South Korean military, and could carry a 2.5 ton payload.

Images in Pyongyang's official Rodong Sinmun newspaper showed smiling officers applauding after the launch, most of them without masks.

Analysts said the latest launch appeared to involve a weapon similar to the one North Korea showed off at a military parade in January

MIT's Vipin Narang said it appeared to be a weapon North Korea displayed at a military parade in January.

"A 2.5 ton warhead will probably settle the question of whether this KN23 variant is nuclear capable. It is," he tweeted.

The United States is stationing 28,500 troops in South Korea to defend it from its neighbor, which it invaded in 1950, while Pyongyang says it needs nuclear weapons to deter a possible US invasion.

- 'Family pattern' -

In addition to Biden's comments came reprimands from Germany, France and Britain, who condemned the evidence as violations of UN Security Council resolutions.

At the request of Washington, the UN sanctions committee on North Korea would meet behind closed doors on Friday, according to diplomatic sources, although a public statement is not expected.

Pyongyang has rapidly advanced its capabilities under Kim's leadership, testing missiles capable of reaching the entire continental United States as tensions escalated in 2017.

Trump's first year in office was marked by a series of escalating pitches, accompanied by a war of words between him and Kim before a dramatic turn toward personal diplomacy, with the two holding headline-grabbing summits in Singapore and Vietnam. .

The United States withdrew some joint military exercises with South Korea while the North froze nuclear tests and ICBM launches.

But its February 2019 Hanoi summit was shattered by sanctions relief and what North Korea would be willing to give up in return.

Communications later ran out, despite a third encounter in the Demilitarized Zone that divides the Korean peninsula, and no substantial progress was made toward denuclearization.

Pyongyang was now "slowly climbing that spectrum, that ladder of the incendiary nature of provocation," said Frank Aum, an expert on North Korea at the US Institute of Peace and a former Pentagon adviser, to see how the administration responded. Biden.

Thursday's launch, and an earlier test of short-range non-ballistic missiles over the weekend, came after joint exercises by the U.S. and South Korean armies and a visit to the region by the U.S. secretary of state. , Antony Blinken, and Secretary of Defense Lloyd Austin. when Blinken repeatedly emphasized the importance of denuclearizing North Korea.

Officials in the Biden administration say they have tried to reach Pyongyang through various channels, but have received no response so far.