South China Sea: US says China's militarisation of islands an act of 'intimidation and coercion”

US Defence Secretary James Mattis has raised the prospect of additional American steps against China if its "militarisation" of the South China Sea keeps apace.

US President Donald Trump, backing the remarks by his Pentagon chief at an international security forum in Singapore, said on Twitter: "Very surprised that China would be doing this?"

Mr Mattis said the Trump administration's recent decision to disinvite China from a multinational naval exercise was an "initial response" to Beijing's island activity.

He called the US action a "relatively small consequence".

"I believe there are much larger consequences in the future," he said.

China's reliance on military muscle to achieve its goals "is not a way to make long-term collaboration the rule of the road in a region that's important to China's future," Mr Mattis said, when asked to elaborate.

"There are consequences that will continue to come home to roost, so to speak, with China, if they don't find a way to work more collaboratively with all of the nations who have interests," he said.

The bluster comes at a delicate time in US-China relations, as the Trump administration is warily asking for China's help with North Korea ahead of a June 12 summit, while also threatening a trade war.

 Mr Trump renewed his threat to hike tariffs on Chinese goods, just days before his commerce secretary arrived in Beijing on Saturday for trade talks.

Mr Mattis said there was little doubt about Beijing's intentions.

"Despite China's claims to the contrary, the placement of these weapons systems is tied directly to military use for the purposes of intimidation and coercion," Mr Mattis said at the annual Shangri-La Dialogue.

Mr Mattis also touched on Taiwan, a longstanding dispute between the US and China.

(Souce: abc.net.au)