US Defense Secretary James Mattis has accused China of "intimidation and coercion" in the South China Sea, taking a tough stance on Beijing at a security summit in Singapore.
Speaking on Saturday at the Shangri-La Dialogue, Mattis said China's militarisation on man-made islands in the South China Sea "stands in stark contrast to the openness of [US] strategy" and "calls into question China's broader goals".
He added there would be "consequences" if China does "not find the way to work more collaboratively with all of the nations who have interest".
Hours after Mattis spoke, Chinese Lieutenant General He Lei lashed out at "irresponsible comments" on China's build-up in the South China Sea.
"Any irresponsible comments from other countries cannot be accepted," he said at the Shangri-La Dialogue.
The comments came on the heels of a string of events that highlight the tension between the world's two biggest economies over the South China Sea's disputed waters.
Last Sunday, Beijing protested what it called a "provocation" after US warships came within 12 nautical miles (around 22km) of the disputed Paracel Islands, among a string of islets, reefs and shoals over which China has territorial disputes with its neighbours.
Earlier that week, the Pentagon withdrew an invitation to China to participate in the world's largest multinational maritime exercise RIMPAC as "an initial response to China's continued militarisation of the South China Sea".
Bomber aircraft
In Singapore, Mattis named deployment of anti-ship missiles, surface-to-air missiles and the recent landing of bomber aircraft at Woody Islands as examples of China's militarisation of "artificial features" in the South China Sea.
"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," the defence secretary said.
He added the acts contradicted Chinese President Xi Jinping's 2015 remarks that there was "no intention to militarise" the Spratly Islands.
In a more conciliatory tone, Mattis said the US would continue to pursue "cooperation whenever possible". He said he would visit Beijing soon at China's invitation.
China is pitted against smaller neighbours in multiple disputes in the South China Sea over islands, coral reefs and lagoons in waters crucial for global trade and rich in fish and potential oil and gas reserves.
It has begun building military structures on disputed islands - much to the dismay of other Southeast Asian nations including the Philippines, Indonesia, Malaysia, Taiwan and Vietnam.
