Mattis visits China amid Korea talks, strategic tensions

US Secretary of Defence James Mattis will make his first visit to China this week amid rising tensions between the two countries but also a deep need for Beijing's support in nuclear talks with North Korea.

Mattis told reporters today he wants to "take measure" of China's strategic ambitions after it positioned weaponry on disputed islets in the South China Sea and is seeking to project its military power deep into the Pacific.

But in a four-day trip that will also include South Korea and Japan, the Pentagon chief also hopes to confirm China's commitment to pressuring North Korea to give up its nuclear weapons, after the historic talks between President Donald Trump and Kim Jong Un in Singapore in early June.

The United States, China, Japan and South Korea "have a common goal: the complete, irreversible and verifiable denuclearisation of the Korean peninsula," Mattis said.

In Beijing From Tuesday to Thursday, Mattis will meet with senior Chinese defence officials.

Then he will travel to Seoul for talks with his South Korean counterpart Song Young-moo, followed by a stop Friday in Japan to see defense chief Itsunori Onodera.

Those meetings are aimed at reassuring both allies that Washington's regional defense commitment remains unchanged after Trump unexpectedly announced on June 12 that the US would suspend a major joint military exercise in South Korea following his meeting with Kim.

The visit to China comes amid bilateral strains that cross multiple sectors. The Trump administration is challenging China on trade, theft of industrial secrets, and cyberthreats. In the defence sector, China's decision to position military hardware in built-up atolls in the South China Sea has sparked new security concerns throughout Southeast Asia.

Signalling Washington's displeasure, in May the Pentagon disinvited China from the 2018 Rim of the Pacific Exercise, in which some two dozen navies train together for mostly civilian missions.

Weeks later at the Shangri-la Dialogue security conference in Singapore, Mattis slammed China for showing contempt of other nations' interests in the South China Sea.

"Despite China's claims to the contrary, the placement of these weapon systems is tied directly to military use for the purposes of intimidation and coercion," Mattis said.

The Chinese, who say the weaponry is only defensive in nature, retorted that Mattis had made "irresponsible comments" that "cannot be accepted."