Aukus, unveiled by the three countries in 2021, is part of their efforts to push back against China’s growing power in the Indo-Pacific region. China has called the pact dangerous and warned it could spur a regional arms race.

‘Natural’ for Japan to play larger Aukus role, but likely not as partner

US President Joe Biden has sought to step up partnerships with American allies in Asia, including Japan and the Philippines, amid China’s historic military build-up and its growing territorial assertiveness.

Rahm Emanuel, the outspoken US ambassador in Tokyo, wrote in an opinion piece in the Wall Street Journal on Wednesday that Japan was “about to become the first additional Pillar II partner”.

A senior US administration official told Reuters on Wednesday that some sort of announcement could be expected in the coming week about Japan’s involvement, but gave no details.

Biden and Japanese Prime Minister Fumio Kishida will likely discuss expanding Aukus to include Japan when the president hosts the prime minister in Washington on Wednesday, a source with knowledge of the talks said.

Australia, however, is wary of beginning new projects until more progress has been made on supplying Canberra with nuclear-powered submarines, said the source, who asked not to be identified because they are not authorised to speak to the media.

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Aukus will ‘get done’, Biden tells Australia’s Albanese during visit to Washington

Aukus will ‘get done’, Biden tells Australia’s Albanese during visit to Washington

Australian Defence Minister Richard Marles “has said publicly, and to Japan, that we will seek opportunities to engage close partners in Aukus Pillar II as our work on critical defence and security capabilities progresses”, a spokesperson said when asked for comment on the FT report.

“Japan is an indispensable defence partner for Australia,” the spokesperson said. “Any engagement of additional countries in Aukus Pillar II projects will be trilaterally decided and announced.”

The White House National Security Council and China’s foreign ministry did not immediately respond to requests for comment on the FT report. The Japanese foreign ministry said it could not immediately comment.

While the US is keen to see Japanese involvement in Pillar II, officials and experts say obstacles remain, given a need for Japan to introduce better cyber defences and stricter rules for guarding secrets.

Kurt Campbell, the US deputy secretary of state and architect of its Indo-Pacific policy, said on Wednesday that the US was encouraging Japan to do more to protect intellectual property and hold officials accountable for secrets.

“It’s fair to say that Japan has taken some of those steps, but not all of them,” he said.

The United States has said for years that other countries in Europe and Asia were expected to join the second pillar of Aukus.

The senior US official said any decisions about who would be involved in Pillar II would be made by the three Aukus members, whose defence ministers had been considering the questions for many months, based on what countries could bring to the project.

Campbell said that other countries had expressed interest in participating in Aukus.

“I think you’ll hear that we have something to say about that next week and there also will be further engagement among the three defence ministers of the United States, Australia, and Great Britain as they focus on this effort as well,” Campbell told the Centre for a New America Security think tank.

‘Wrong path’: China warns New Zealand over Aukus security cooperation

Campbell also said on Wednesday that the Aukus submarine project could help deter any move by Beijing against Taiwan.

Beijing sees Taiwan as part of its territory to be united with the mainland, by force if necessary. Most countries, including the US, do not recognise Taiwan as independent but Washington opposes any attempt to take the island by force and remains committed to supplying it with weapons.