President Biden and the leaders of the United Kingdom (U.K.) and Australia on Wednesday announced a new trilateral security partnership focused on the Indo-Pacific, a veiled effort to confront China’s growing power in the region.

As part of the new partnership, named AUKUS for its members, the three countries are launching an 18-month review to explore how Australia can best acquire nuclear-powered submarines — technology that is quieter, is faster and has more endurance than conventional submarines.

A senior Biden administration official stressed the rarity of the engagement, noting that the U.S. has shared nuclear propulsion capability with only one other nation — the U.K. — as part of an agreement in 1958.

“This is an historic announcement. it reflects the Biden administration’s determination to build stronger partnerships to sustain peace and stability across the entire Indo-Pacific region,” the official told reporters on a call Wednesday previewing the announcement. “This new architecture is really about deepening cooperation on a range of defense capabilities for the 21st century.”

Officials insist that the new partnership is not about one particular country but rather about the U.S. commitment to maintaining stability and upholding the “international rules-based order” in the Indo-Pacific. Indeed, none of the three leaders explicitly mentioned China in their remarks outlining the new partnership.

The announcement also comes as the Biden administration is looking to bolster its alliances after four years of former President Trump’s “America first” foreign policy and the more recent chaotic U.S. exit from Afghanistan under Biden.

Biden, British Prime Minister Boris Johnson and Australian Prime Minister Scott Morrison detailed the new partnership during remarks Wednesday afternoon. Biden spoke from the White House East Room, while the other leaders’ remarks were carried virtually.

“The future of each of our nations and indeed the world depends on a free and open Indo-Pacific enduring and flourishing in the decades ahead,” Biden, who stood in front of flags from each of the three nations, said in prepared remarks. “This is about investing in our greatest source of strength — our alliances — and updating them to better meet the threats of today and tomorrow.”

“This initiative is about making sure that each of us has a modern capability, the most modern capabilities we need to maneuver and defend against rapidly evolving threats,” Biden continued, noting that it will bring together “our sailors, our scientists and our industries to maintain and expand our edge in military capabilities and critical technology.”

Officials said that the new partnership will include deepened cooperation between the U.S., U.K. and Australia across emerging security areas such as cyber, artificial intelligence, quantum technology and undersea capabilities. The three nations will work to improve information and technology sharing.

The officials insisted that the U.S. remains committed to nonproliferation and that the new dialogue on nuclear-powered submarines is not about Australia seeking nuclear weapons.

“This partnership is in many ways possible because of Australia’s longstanding and demonstrated commitment to nuclear nonproliferation,” a second senior administration official said, noting the countries would be engaged with the International Atomic Energy Agency.

It’s unclear how long it will take for Australia to develop the capability. Morrison during his remarks said that Australia would build the submarines in Adelaide “in close cooperation with the United Kingdom and the United States.”

Biden has made addressing competition and aggression from China a central focus of his foreign policy. While Biden has sought a less confrontational relationship with Beijing, he has made a point of calling out China publicly for what the U.S. views as unacceptable behavior. Tensions have percolated between the two countries on various fronts, including the coronavirus pandemic, human rights and economic issues.

The first senior administration official said Wednesday that the new partnership is not “aimed at any one country” but rather part of a broader effort by the U.S. to promote peace and stability in the Indo-Pacific. 

“One of the things that the United States has done most effectively in the Indo-Pacific is to secure peace and stability and to be the ultimate guarantor of that rules-based order. I think it would be fair to say over the last several years that there have been questions. Does the United States still have the stomach? Do we have the wisdom that we want to continue to play that role?” the official said, an apparent reference to Trump’s treatment of U.S. allies.

“What President Biden is saying with the initiative is count us in,” the official said. “We are all in for a deeper sustained commitment to the Indo-Pacific, and we recognize that one of our critical roles is indeed the maintenance of peace and stability there.”

China’s embassy in Washington reacted to news of the pact saying the countries involved should "shake off their Cold-War mentality and ideological prejudice," according to Reuters.

Chinese embassy spokesman Liu Pengyu told Reuters countries "should not build exclusionary blocs targeting or harming the interests of third parties. In particular, they should shake off their Cold-War mentality and ideological prejudice."

The U.S. military periodically sends warships and plans to the South China Sea region to promote freedom of navigation in the region.

Biden has looked to other partnerships to demonstrate U.S. commitment to allies in the Indo-Pacific. The president will host the first leader meeting of the so-called Quad alliance — a relatively new group comprised of the U.S., Australia, India and Japan — at the White House next week.

Last Thursday, the president spoke by phone with Chinese President Xi Jinping, their second call since Biden took office in January. Biden emphasized the U.S. commitment to playing a role in the Indo-Pacific, the senior administration official said Wednesday, but did not specifically discuss the new AUKUS initiative.

Updated: 5:39 p.m.