The US State Department's number two diplomat has suggested the AUKUS submarine project between Australia, Britain and the US could help deter any Chinese move against Taiwan.
The project, unveiled by the three countries in 2023, involves Australia acquiring nuclear-powered attack submarines as part of the allies' efforts to push back against China's growing power in the Indo-Pacific region.
But the three countries have been reluctant to publicly tie AUKUS to growing tensions over Taiwan, the democratically governed island claimed by China as its territory, with Australia saying it did not promise to support the US in any Taiwan military conflict.
US Deputy Secretary of State Kurt Campbell made a rare linkage between Taiwan and AUKUS, telling Washington's Centre for a New American Security think tank that new submarine capabilities would enhance peace and stability, including in the strait that separates China and Taiwan.
AUKUS' submarine capabilities "have enormous implications in a variety of scenarios, including in cross-strait circumstances," Campbell said.
"I would argue that working closely with other nations, not just diplomatically but in defence avenues, has the consequence of strengthening peace and stability more generally," he added.
China has called the AUKUS pact dangerous and warned it could spur a regional arms race.
US President Joe Biden has sought to step up partnerships with allies in Asia, including Japan and the Philippines, amid China's historic military build-up and its growing territorial assertiveness.
Biden will host Japanese Prime Minister Fumio Kishida and Philippines President Ferdinand Marcos Jr for a summit in Washington on April 11, and meet Kishida for a bilateral summit the day before.
Campbell said the meetings will mark a "massive modernisation" of the US-Japan relationship and more engagement among the three countries including in the South China Sea, where Washington has criticised the Chinese coastguard's use of water cannons on Philippine vessels near the disputed Second Thomas Shoal.
"There will be an unprecedented trilateral engagement ... you will see commitments on all three nations that involve closer co-ordination and engagement in the South China Sea and elsewhere," Campbell said.
The summit with Japan would bring an "historic" updating of the security partnership, and steps "that will allow the United States and Japan to work more collaboratively on joint development, and potentially co-production, of vital military and defence equipment," Campbell said.
On Ukraine, he said the US government has assessed that China helped Moscow "retool" and Russia "almost completely reconstituted militarily" after early setbacks in the Ukraine war.
