China and other nations must strengthen efforts to curb North Korea's nuclear weapons programme, LIS Secretary of State Rex Tillerson said yesterday, while also calling out Beijing over its South China Sea activities.

America's top diplomat, speaking after talks in Sydney, also gave a brief response to the unfolding crisis in the Gulf, where Saudi Arabia, Bahrain, the United Arab Emirates and Egypt have all announced they are severing ties with gas-rich Qatar.

In the Asia-Pacific region, the United States has spent recent weeks trying to reassure allies it can maintain a tough line against China's "militarisation" of the South China Sea while at the same time seeking help from Beijing.

President Donald Trump - who frequently denounced China on the campaign trail - has turned to Beijing to help rein in ally North Korea's weap- ons programme, prompting concern among Asian allies that America might go easy on the South China Sea territorial dispute.

"We desire productive relationships," Tillerson said after annual discussions with his Australian coun-

terpart Julie Bishop in Sydney.

"But we cannot allow China to use its economic power to buy its way out of other problems, whether it's militarising islands in the South China Sea or failing to put appropriate pressure on North Korea." He said China and other regional partners should "step up" efforts to help solve the North Korea situation, because it presents a threat to the "entire world."

China claims nearly all of the South China Sea despite partial counterclaims from Taiwan, the Philippines, Brunei, Malaysia and Vietnam.

It has rapidly built reefs into artificial islands capable of hosting military planes.

Tillerson reiterated US and Australian commitment to freedom of navigation in the South China Sea to "ensure unimpeded flow of lawful commerce in a rules-based order".

But reporters asked Tillerson if America was applying a double standard in telling countries to adhere to the international order while simultaneously pulling out of a trans-Pacific trade deal and the Paris climate accords -- moves that prompted even longstanding allies to question whether America was retreating into isolationism.