WASHINGTON (AP) — The United States and Japan unveiled plans Wednesday to strengthen their alliance to help counter threats from North Korea and China, which they called the greatest security challenge in the region.

In unusually blunt terms, the U.S. and Japanese foreign and defense ministers condemned China’s increasing aggressiveness in the Indo-Pacific and elsewhere, called out Russia for its war with Ukraine and castigated North Korea for ramping up its nuclear and missile programs.

In a joint statement, Secretary of State Antony Blinken, Defense Secretary Lloyd Austin and their Japanese counterparts, Yoshimasa Hayashi and Yasukazu Hamada, said China presents an “unprecedented” threat to international order and vowed to redouble their efforts to counter it.

“China’s foreign policy seeks to reshape the international order to its benefit and to employ China’s growing political, economic, military, and technological power to that end,” the statement said. “This behavior is of serious concern to the alliance and the entire international community, and represents the greatest strategic challenge in the Indo-Pacific region and beyond.”

The four men agreed to adjust the American troop presence on the island of Okinawa in part to enhance anti-ship capabilities that would be needed in the event of a Chinese incursion into Taiwan or other hostile acts in the South or East China seas.

They also added a formal mention of outer space in the longstanding U.S.-Japan security treaty, making clear that “attacks to, from and within space” could trigger the mutual defense provisions of the treaty. That had previously been outside the scope of the agreement. In addition, the U.S. space agency NASA plans to sign a cooperation deal with Japan on Friday, they said.

Prior to the meeting, Japan’s defense ministry announced it was ready to start construction on an uninhabited island where the two militaries will hold joint military exercises beginning in 2027.

Blinken said the agreement signed Wednesday reflects the two nations’ effort to deepen cooperation “across all realms,” including space, cybersecurity and emerging technologies.

He said the U.S.-Japan alliance has “been the cornerstone of peace and stability in the Indo-Pacific, ensuring the security, the liberty and prosperity of our people and people across the region.”

Wednesday’s discussions will be followed by a meeting on Friday between President Joe Biden and Japanese Prime Minister Fumio Kishida at which they will underscore the importance of the relationship.

Kishida, on a weeklong trip to visit allies in Europe and North America, signed a defense agreement with British Prime Minister Rishi Sunak on Wednesday that strengthens military ties between their two counties, also in response to China.

Austin noted that Wednesday’s agreement affirms America’s “ironclad commitment to defend Japan with a full range of capabilities, including nuclear” and underscores that Article 5 of the mutual security treaty applies to the Senkaku Islands. The disputed islands outside Japanese territorial waters are also claimed by Beijing.

Earlier Wednesday, Japan said it would begin constructing a pair of runways on the small southern island of Mageshima where joint exercises, including those of F-35B stealth fighters, amphibious operations and missile interception, will start in roughly four years.

The island, off the southwestern coast of Kagoshima on the southernmost main island of Kyushu, will be a hub for troop deployment and munition supply in case of a conflict like a Taiwan emergency.

Japan and the United States are moving one of their key flight exercise sites to the southern island, which is much closer to the U.S. air base of Iwakuni, home to an F-35B fleet, than the current training site on Iwo Jima, where one of the bloodiest and most iconic battles of World War II was fought.

The changes in the U.S. deployment on Okinawa will transform the 12th Marine Regiment into a smaller, more rapidly mobile unit — the 12th Marine Littoral Regiment, which will be designed to be better equipped to fight an adversary and defend the U.S. and its allies in the region.

Austin said the regiment will bring “tremendous” capabilities to the region as a “more lethal, more agile, more capable” military unit.

U.S. officials said the decision will not increase the number of Marines on the island and does not come with any significant change in weapons capability.

Reinforcement of military capability or troops is a sensitive issue for Okinawa, site of one of the bloodiest ground battles at the end of World War II. The island hosts more than half of the U.S. troops based in Japan, and Okinawans want that number reduced.

A littoral regiment is made up of roughly 2,000 Marines, and includes a combat team with an anti-ship missile battery, a logistics battalion and an air defense battalion. The current Marine regiment on Okinawa that it would essentially replace includes about 3,400 Marines and sailors.

Wednesday’s agreements follow Japan’s announcement last year that it would increase its defense spending to 2% of gross domestic product over five years. That would make its defense budget the world’s third-largest — a dramatic shift in Tokyo’s priorities that reflects growing concerns about North Korea and potential Chinese military action against Taiwan.

“Japan is stepping up big time and doing so in lockstep with the United States, partners in the Indo-Pacific, and in Europe,” national security adviser Jake Sullivan said, adding that Biden’s engagement with allies is “paying huge dividends” for global security.

While there is a growing fear of a Taiwan emergency, many in the region are concerned that defense buildups by both China and the U.S. and its allies could increase the risks of getting embroiled in war.

In their talks on Friday, Biden is expected to raise with Kishida the case of Lt. Ridge Alkonis, a U.S. Navy officer deployed to Japan who has been jailed after pleading guilty last year to the negligent driving deaths of two Japanese citizens in May 2021, according to a senior administration official.

The official, who requested anonymity to discuss negotiations with the Japanese, said the administration is working “to find a compassionate resolution that’s consistent with the rule of law.”

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Associated Press writers Aamer Madhani in Washington and Mari Yamaguchi in Tokyo contributed to this report.