The United States and Japan on Friday voiced strong concern about China's growing might and pledged to work together to push back against attempts to destabilise the region, including against emerging defence threats.
The comments from the two allies, in a joint statement that followed a virtual "two-plus-two" meeting of their foreign and defence ministers, highlights how deepening alarm about China - and increasing tension over Taiwan - have put Japan's security role in greater focus.
In their meeting, the ministers expressed concerns that China's efforts "to undermine the rules-based order" presented "political, economic, military and technological challenges to the region and the world," the joint statement said.
"They resolved to work together to deter and, if necessary, respond to destabilising activities in the region," it said.
The ministers also said they had "serious and ongoing concerns" about human rights issues in China's Xinjiang and Hong Kong regions and underscored the importance of peace and stability in the Taiwan Strait.
While pacifist Japan retains close economic ties to China, there is growing concern in Tokyo about a potential move by Beijing against democratic Taiwan.
"This is clearly a combined message reflecting a common concern, not a case of US arm-twisting to get Japan to sign onto vague euphemisms," said Daniel Russel, who served as the top US diplomat for Asia under Obama and is now with the Asia Society Policy Institute.
"In particular, the expression of joint resolve to respond if necessary to destabilising activities comes across as a powerful expression of alliance solidarity and determination."
Earlier, US Secretary of State Antony Blinken said the two countries would sign a new defence collaboration deal to counter emerging threats, including hypersonics and space-based capabilities.
Blinken said the US- Japan alliance "must not only strengthen the tools we have, but also develop new ones", citing Russia's military buildup against Ukraine, Beijing's "provocative" actions over Taiwan and North Korea's latest missile launch. North Korea fired a "hypersonic missile" this week that successfully hit a target, its state news agency said.
Following the meeting, Japan's foreign minister, Yoshimasa Hayashi, said Tokyo had explained its plan to revise the national security strategy to fundamentally boost defence capabilities, which he said was strongly supported by his US counterparts.
Prime Minister Fumio Kishida in October promised to revise Japan's security strategy to consider "all options including possession of the so-called enemy-strike capabilities".
Kishida's government has approved record defence spending, with a 10th straight annual increase in 2022.
Jeffrey Hornung, a Japanese security policy expert at the Rand Corporation, a US-backed think tank, said while options for Japan to use force are realistically limited, a Taiwan emergency would be one potential scenario that Japan could deem as threatening its survival.
"There is no coded messaging here," Hornung said.
"China is the challenge and they said as much, then detailed all the ways the alliance is determined to work to counter its destabilising activities."