SUMMIT COLLAPSE MAY STRAIN US-CHINA TIES

US President Donald Trump's cancellation of a summit with North Korean leader Kim Jong Un threatens further strain on US-China ties amid a trade dispute that had been intertwined with Beijing's pressure on isolated Pyongyang.

The United States and China are also increasingly at odds in the disputed South China Sea. The Pentagon this week withdrew an invitation for China to take part in a major naval exercise in Hawaii, and Beijing has ramped up pressure on self-ruled Taiwan, armed by Washington but claimed by Beijing.

Trump on Thursday released a letter to Kim announcing his withdrawal from the planned June 12 meeting in Singapore, which would have been the first between leaders of the two countries.

Although Chinese state media called for continued engagement between Washington and Pyongyang, Trump's move could mark a split between China and the United States over how to deal with North Korea and its nuclear weapons, experts said.

It also risks adding fuel to simmering trade tensions, just days after China and the United States pulled back from the brink of a full-blown trade war.

Trump said yesterday that the meeting with Kim Jong Un could still go ahead. US Defense Secretary Jim Mattis told reporters diplomats were "still at work" and said Trump had just sent a note out on the summit, which could be back on "if our diplomats can pull it off."

CHINA ALIGNED WITH KIM

China has long viewed North Korea as a useful buffer between it and US forces in South Korea. The two also have deep emotional ties; Chinese troops fought side-by-side with North Korea in the 1950-53 Korean War.

But in recent years, relations between China and North Korea had nosedived to the point of a near diplomatic freeze, as Beijing signed on to ever-stricter United Nations sanctions over Pyongyang's nuclear and ballistic missile programmes.

China's willingness to keep up pressure on its neighbour may now wane.

Even with the summit's collapse, China must continue to improve ties with North Korea given Kim's pledge not to carry out nuclear and missile tests, China's widely read state-run Global Times tabloid said in an editorial yesterday.

TRADE DEAL UNCERTAINTY

Meanwhile, Trump also cast uncertainty over progress in trade talks, saying Wednesday that Washington would seek a new "structure" for the deal and a new direction for talks with Beijing, days after the two had taken conciliatory stances. US Commerce Secretary Wilbur Ross will visit China from June 2 to 4.

"China does not link trade and North Korea because that will make things more complicated," said Ruan Zongze, a former diplomat now with the China Institute of International Studies, a think tank linked to China's foreign ministry.

Some analysts had suggested, however, that China was using its leverage on North Korea, and Trump's perceived desire for a successful summit with Kim, to blunt the sharpest edges of US trade threats.

Tu Xinquan, dean of the China Institute for WTO Studies at the University of International Business and Economics in Beijing, said the summit's collapse added to uncertainty in US-China trade relations.

"Even before this announcement, Trump's attitude on trade with China had changed a bit," he said. "I am a little pessimistic about this trade deal."

A souring of relations could see a tougher line from Washington on other issues deemed sensitive in Beijing, analysts say.