(Washington) US President Joe Biden and his South Korean counterpart Yoon Suk Yeol on Wednesday issued a solemn warning to North Korea against any nuclear attack that would bring about the “end” of the regime in Pyongyang.

Speaking at a press conference after their meeting at the White House, the two leaders issued repeated warnings to the northern neighbor, highlighting the strengthening of their means of deterrence and their “alliance steadfast,” “forged in wartime and flourished in peacetime,” according to Mr. Biden.

“A nuclear attack by North Korea against the United States or its allies or partners is unacceptable and will bring about the end of any regime that decides to take such action,” warned the American president.

The United States and South Korea thus agreed in a Washington Declaration adopted on Wednesday to significantly strengthen their defense cooperation, including nuclear, through closer “consultations”.

“Our two countries agreed to initiate immediate bilateral consultations in the event of a North Korean nuclear attack and promised to respond promptly and decisively using the full force of our alliance, including the nuclear weapons of the United States,” Mr. Yoon said.

It is thus for the United States to strengthen its security umbrella and reassure its South Korean ally, North Korea having launched a record level of ballistic missile fire this year.

The message is also addressed to China, which the United States considers to be its main strategic challenge for the coming decades.

It comes as the United States has recently significantly strengthened its defense relations with Australia, Japan and the Philippines.

President Yoon, who is on a six-day state visit to the United States, arrived to the cheers of a few hundred people gathered outside the White House and received military honors in a well-rehearsed ceremony.

The “occasional” deployment of the nuclear-tipped ballistic missile submarine is among the key measures of a “Washington Declaration” to be adopted by the two leaders on Wednesday.

The two leaders must still participate with their wives in a gala dinner in the evening.

This is only the second state visit by a foreign leader under President Biden, following that of French President Emmanuel Macron last December.

Among the measures decided within the framework of this Washington Declaration is the stopover of a nuclear-powered ballistic missile submarine in South Korea for the first time in four decades.

The deployment of this submarine equipped with nuclear-tipped ballistic missiles, however, must remain “occasional”.

In addition, this Washington Declaration sets up a mechanism for consultation and exchange of information with Seoul on nuclear deterrence.

However, the United States has no intention of permanently deploying nuclear weapons in South Korea and Seoul reaffirms its commitment not to seek to acquire its own arsenal.

For the United States, it is a question of making “our deterrent system more visible through the deployment at regular intervals of strategic means”, said the official.

Besides the submarines, there will be “a regular cadence of visits from bombers and aircraft carriers”. But there will be no “permanent deployment of these assets or nuclear weapons,” he said.

The American authorities had warned China beforehand in order to explain to them “the reasoning” behind these measures, while Beijing is likely to denounce a new escalation in the region.

President Yoon is scheduled to address both houses of Congress on Thursday and participate in a luncheon with Vice President Kamala Harris and Secretary of State Antony Blinken. On Friday, he will travel to Boston to visit the prestigious universities of MIT and Harvard, before returning to Korea on Saturday.

Arriving in the capital on Monday, he went to NASA’s Goddard Space Center near Washington on Tuesday, then accompanied President Biden to the Korean War Memorial (1950-53) in the center of the capital.