Next week, Mr. Biden will gather the leaders of “the Quad” — an informal partnership of the United States, Japan, India and Australia — at the White House for an in-person meeting, another way to demonstrate common resolve in dealing with Beijing.
Mr. Biden spoke with President Xi Jinping of China last week for roughly 90 minutes, only the second time the two leaders have spoken in since Mr. Biden took office. Few details of the conversation were revealed, so it is unclear whether Mr. Biden gave his Chinese counterpart warning of the move with Australia. But none of it would have come as a surprise to Beijing; earlier, the Australians had announced a deal with France for less technologically sophisticated submarines. That deal collapsed.
Nonetheless, the decision to share the technology for naval reactors, even to a close ally, was a major move for Mr. Biden — one bound to raise protests by China and questions from American allies and nonproliferation experts. The United States last shared the nuclear propulsion technology with an ally in 1958 in a similar agreement with Britain, administration officials said.
“There is a shared understanding that we need to strengthen deterrence and actually be prepared to fight a conflict if one occurs,” said Bonnie Glaser, director of the Asia program at the German Marshall Fund, a policy think tank. “It reflects growing concern about Chinese military capabilities and intentions.”
The nuclear reactors that power American and British submarines use bomb-grade, highly enriched uranium, a remnant of Cold War-era designs. And for two decades, Washington has been on a drive to eliminate reactors around the world that use bomb-grade fuel, substituting them with less dangerous fuel to limit the risk of proliferation.
The movement gained momentum after the Sept. 11 attacks. President Barack Obama ran a series of “nuclear summits” for world leaders, used to pressure nations to remove from service old reactors that used highly enriched uranium so that the fuel could never fall into the hands of terrorists.
But the arrangement with Australia seems almost sure to move in the other direction: Australia is likely to power its submarines with highly enriched uranium, because for now, there is little choice. Aware of the contradiction, administration officials cast the decision as an “exception,” though one they would not make for other major allies. That includes South Korea, which in decades past was caught moving toward building its own nuclear arsenal. Australia has been a leader in the nonproliferation movement.