The Asia Reassurance Initiative Act, which US President Donald Trump signed into law this week, signalled that the US wanted to retain its allies and mobilise them to counter China if necessary, the observers said.

Collin Koh, a maritime security specialist at Nanyang Technological University in Singapore, said that despite a recent easing tensions, the act’s broad regional scope meant “we would likely see gradual effects impinging on Sino-US rivalry in Southeast Asia”.

“We can’t underestimate the potential ramifications of [the act] contributing to the sharpening of the Sino-US rivalry, even if it’s still quite another matter whether the Trump administration will truly follow up,” Koh said.

Beijing and Washington are increasingly at odds over the South China Sea, a strategic waterway through which billions of dollars in trade passes each year. Each country has sent warships and military aircraft through the contested waters in patrols that have led to at least one near miss.

According to the act, to US will reaffirm security commitments to its allies in the Indo-Pacific region, including Japan, South Korea and Australia, and spend US$1.5 billion annually for five years to improve its regional presence. It will also build security partnerships in Southeast Asia.

Part of the strategy will be conducting freedom of navigation operations with those allies in the East and South China seas, missions that Beijing sees as an excuse for the US to flex its military muscle.

The act also authorises the US to impose penalties on entities and governments for stealing intellectual property – another major source of friction between China and the US.

The rivalry between China and the US has triggered concerns in the region, with Singapore’s prime minister, Lee Hsien Loong, warning in November that Southeast Asian nations might be forced to choose between China and the US.

Koh said the involvement of US regional allies would likely create a bigger headache for China.

“Where it comes to difficulty to be possibly encountered by China, it’s plausible to envisage that the strategic pressure may not emanate only from the US per se, since [the act] also appears to emphasise the role played by US allies and partners,” he said.

Tony Nash, head of research firm Complete Intelligence, said the signing of the act meant the “US has friends”.

“And that those friends aren’t necessarily based on a multibillion-dollar loan commitment, but on ongoing political, economic and military commitments. It’s presenting a stark reality to the very transactional relationships China is building through the Belt and Road [Initiative],” he said, referring to Beijing’s massive international infrastructure and trade push. “This bill is demonstrating the US’ commitments to the region.”

The signing of the act comes as the clock ticks on a 90-day truce for Washington and Beijing to negotiate an end to their trade war.

Two days of vice-ministerial-level talks are set to start in Beijing on Monday, with China hoping to secure some relief from US tariffs on Chinese goods, duties that are starting to weigh on its already slowing economic growth.

At the same time, Chinese President Xi Jinping has reaffirmed that Beijing will not abandon the use of force in seeking unification with Taiwan.

But analysts said the act was not a tactic to pressure China to make trade concessions.

“It’s less of a challenge to China than a commitment to other parts of Asia. It doesn’t focus on China, it namechecks almost every other country in Asia,” Nash said.