Kamala Harris accuses China of 'intimidation' in disputed seas

US vice president Kamala Harris accused China on Tuesday of intimidation in disputed Asian waters, seeking to rally regional allies as the United States' superpower status takes a hit in Afghanistan.

Her comments in Singapore came as Washington seeks to reset relations in Asia after the turbulent Donald Trump era and build a bulwark against the rising might of Beijing.

But her trip to the region, which also includes a stop in Vietnam, comes as Washington faces fresh questions over its dependability amid the US pullout from Afghanistan and Taliban takeover.

In a speech laying out her administration's foreign policy goals, Harris reiterated that Washington had "enduring commitments" in Asia -- and took aim at China.

"Beijing continues to coerce, to intimidate and to make claims to the vast majority of the South China Sea," she said.

"Beijing's actions continue to undermine the rules-based order and threaten the sovereignty of nations.

"The United States stands with our allies and partners in the face of these threats."

China claims almost all of the resource-rich sea, through which trillions of dollars in shipping trade passes annually, with competing claims from four Southeast Asian states as well as Taiwan.

Beijing has been accused of deploying a range of military hardware including anti-ship and surface-to-air missiles there, and ignored a 2016 international tribunal decision that declared its historical claim over most of the waters to be without basis.

Tensions have escalated recently between Beijing and rival claimants, with Manila angered after hundreds of Chinese boats were spotted at a contested reef while Malaysia scrambled jets to intercept Chinese military aircraft.

Harris also sought to allay fears that growing US-China tensions could force countries which have strong ties with both of the world's top economies to choose sides.

"Our engagement in Southeast Asia and the Indo-Pacific is not against any one country, nor is it designed to make anyone choose between countries," she said.

Harris is the latest top official from president Joe Biden's administration to visit the region. On a trip to Singapore last month, Pentagon chief Lloyd Austin also strongly criticised China's maritime claims.

But the Afghan crisis and doubts about US credibility are casting a long shadow over Harris's visit.

In Tuesday's speech, she defended Biden's decision to push ahead with the US pullout from Afghanistan as "courageous and right" and reiterated US officials were "laser-focused" on the chaotic evacuation from Kabul airport.

"The United States has been focused on safely evacuating American citizens, international partners, Afghans who worked side by side with us, and other Afghans at risk," she said.

Harris also announced that Washington was offering to host the annual meetings of the Asia-Pacific Economic Cooperation (APEC) forum in 2023, a grouping that includes Beijing and the US.

The US-China relationship has deteriorated over a range of issues from cyber security and tech supremacy to human rights in Hong Kong and Xinjiang.

Biden has largely continued Trump's hawkish stance on China, describing the Asian power as the pre-eminent challenge to the United States, but has lowered the temperature.

Singapore and the US have long enjoyed strong ties, and the city-state is the anchor of the American naval presence in Southeast Asia.

The vice president will hold talks Tuesday with business leaders in Singapore on supply chain issues, including the global microchip shortage, before heading to Hanoi.

She has been criticised for visiting Vietnam amid the Afghan evacuation, which has prompted comparisons with the trauma of 1975 in Saigon, when US helicopters ferried final evacuees from the embassy roof.