President Biden and Prime Minister Fumio Kishida of Japan announced a range of moves on Wednesday to further enhance military, economic and other cooperation between the two longtime allies as part of the president’s efforts to counter China’s aggressive actions in the Indo-Pacific region.

During a pomp-filled ceremony honoring the visiting Japanese prime minister, the president said the United States and Japan would create an expanded defense architecture with Australia, participate in three-way military exercises with Britain and explore ways for Japan to join a U.S.-led coalition with Australia and Britain.

Mr. Biden also announced that the United States would take a Japanese astronaut to the moon as part of NASA’s Artemis program, which would be the first time a non-American has set foot on the moon.

“This is the most significant upgrade of our alliance since it was first established,” Mr. Biden said at a news conference in the White House Rose Garden along with the prime minister.

Mr. Kishida made a point of reaffirming Japan’s “strong support for Ukraine” in its war against Russia, a key priority for Mr. Biden, and framed the European conflict in terms of the precedent it could set in Japan’s neighborhood. “Ukraine today may be East Asia tomorrow,” Mr. Kishida said.

Mr. Biden’s statements on Wednesday fit into a long history of American presidents declaring that the U.S.-Japan relationship was the most important bilateral alliance in the world.

In preparation for the state visit, Mr. Biden’s aides described the closer military link as one of the biggest upgrades of the U.S.-Japan Security Treaty, which dates back to early 1960, an Eisenhower-era innovation to turn a former World War II enemy into what later presidents called America’s “biggest aircraft carrier in the Pacific.”

There has always been a bit of hyperbole to the statement. But as the perceived threat from China has grown, Japan has been the linchpin of broader U.S. efforts to unify its separate allies in the region — especially South Korea and the Philippines — into a coordinated force.

The prime minister’s visit comes at the same time Mr. Biden is strengthening the American partnership with the Philippines, which also finds itself the target of a mounting Chinese military presence in the South China Sea. On Thursday, Mr. Biden and Mr. Kishida will meet with President Ferdinand Marcos Jr. of the Philippines to demonstrate their joint commitment.

The day began with a welcoming ceremony on the South Lawn, where Mr. Biden hailed the relationship between the United States and Japan as a “cornerstone of peace, security, prosperity” and said that President Eisenhower’s promise of an “indestructible partnership” had been achieved.

“Just a few generations ago, our two nations were locked in a devastating conflict,” Mr. Biden said after he and Mr. Kishida watched a procession of U.S. military honor guards upon the prime minister’s arrival at the White House. “It would have been easy to say we remain adversaries. Instead, we made a far better choice: We became the closest of friends.”

The Biden administration signaled the importance of its relationship with Tokyo by holding an official state dinner on Wednesday evening in honor of Mr. Kishida, something reserved for America’s closest allies.

The visit comes amid hand-wringing in Washington and Tokyo over the possibility of a return to power by former President Donald J. Trump, whose unpredictable foreign policy kept many world leaders on edge. One goal for Mr. Biden, officials said, is to create as much permanence in the Japanese relationship as possible before the election in November.

One administration official, speaking on the condition of anonymity to discuss the upcoming meeting, said there was “anxiety in capitals” around the world, including in Tokyo, about whether Mr. Trump would continue the international engagement that Mr. Biden and prior presidents have embraced. Another official said there was a real risk that Mr. Trump, if re-elected, could move to undo what the leaders of the two countries announced on Wednesday.

Mr. Biden and Mr. Kishida outlined greater coordination and integration between the military forces of both countries, including the formation of a joint defense council that could support more defense-related exports of equipment produced in Japan. And officials agreed on new cooperation on ventures in space and collaboration between research institutions working on artificial intelligence, semiconductors and clean energy.

“The American alliance system has helped bring peace and stability to the Indo-Pacific for decades, and now we need to update and upgrade that alliance network for the modern age,” said Jake Sullivan, the White House national security adviser. “It goes way beyond security. It’s economics. It’s technology. It’s infrastructure development. And it’s diplomacy. And that’s all going to be on display in the meeting with the prime minister.”

Rahm Emanuel, the United States ambassador to Japan, called the meeting a chance for the two nations to go beyond America’s work to protect Japan and to “write the first chapter of the next era” of cooperation as they work together to project power throughout the region.

That would be a more far-reaching relationship than the United States has historically had with Japan, which for decades after World War II restricted its spending on defense and its engagement around the world.

That began to change during the past several years, under Mr. Kishida, who pushed to expand defense spending and participate in global efforts like the sanctions on Russia for its invasion of Ukraine. Administration officials said Japan’s new willingness to become a full partner with the United States on the global stage has taken the alliance between the two countries to a new level.

But there are still some tensions. The two leaders had to dance carefully around Mr. Biden’s reluctance to let a Japanese firm buy a storied U.S. steel maker. That struck national security experts as strange, since such deals are usually blocked only when they give critical technology to adversaries, not allies.

“The idea that you block the acquisition of a company by one of your closest allies makes no sense in alliance-building terms,” said Joseph S. Nye Jr., an emeritus professor at Harvard who designed many of the defense cooperation strategies with Japan in the Clinton administration.

The meeting on Thursday between Mr. Biden, Mr. Kishida and Mr. Marcos represents a more aggressive effort by the United States and its allies to isolate China — rather than allowing the Chinese leadership to intimidate and isolate its neighbors in the South China Sea and elsewhere.

The Thursday meeting will be the first time that the leaders of the three nations have met together, officials said.

“We’re continuing to deepen our cooperation with our closest partners to ensure what we’ve talked about many times from this podium and elsewhere: a free, open and prosperous Indo Pacific,” Mr. Sullivan told reporters during a briefing at the White House on Tuesday.

Mr. Sullivan declined to say whether Mr. Biden would raise with Mr. Kishida the issue of plans by Nippon Steel, a Japanese corporation, to acquire U.S. Steel, the struggling manufacturer based in Pittsburgh. Mr. Biden has publicly said that he will have “the backs” of union steel workers, indicating his opposition to the deal.

“You guys all know Joe Biden,” he said. “You’ve seen Joe Biden. He’s been very clear that he’s going to stand up for American workers. He’s going to defend your interests. He’s also been very clear that he is going to make sure that the U.S.-Japan alliance is the strongest it’s ever been.”

But administration officials said later on Tuesday that they did not think the subject would come up between the two leaders on Wednesday because both men already know the position of the other.

Mr. Biden greeted Mr. Kishida on Tuesday evening for a brief arrival at the White House. Later, the two leaders and their wives went to BlackSalt, an upscale seafood restaurant in Washington, for a more casual dinner ahead of the formal events on Wednesday.

White House officials said the couples had exchanged a series of gifts on Tuesday evening, a diplomatic tradition for such events. The official gift from Mr. Biden and Jill Biden, the first lady, was a three-legged table that was handmade by a Japanese American-owned company in Pennsylvania.

Other gifts included a lithograph and a two-volume LP set autographed by Billy Joel and a vintage vinyl record collection. Dr. Biden gave Ms. Kishida a framed painting of the Yoshino cherry tree that the two had planted on the South Lawn last spring, and a soccer ball signed by the U.S. women’s national soccer team and the Japanese women’s team.

At the state dinner, the White House was scheduled to serve a meal that would include house-cured salmon and dry-aged rib-eye steak with blistered shishito pepper butter.

David E. Sanger contributed reporting.