US President Donald Trump says he wants China to help deal with its close ally Russia as he tries to negotiate peace in Ukraine.

Trump has left the US for a five-day trip to Malaysia, Japan and South Korea, his first to the region and longest journey abroad since taking office in January.

The Republican leader hopes to lock in trade, critical mineral and ceasefire deals before turning to the toughest challenge — a face-to-face with China’s Xi Jinping on Thursday in South Korea.

On Sunday (AEDT), Trump told reporters he would like China to help deal with its close ally Russia as the war rages in Ukraine.

“I’d like China to help us out with Russia,” the US president said on Air Force One.

Trump is also working to maintain the signature foreign policy achievement of his second term, a fragile ceasefire he helped to strike in the Israel-Gaza conflict, while the Russian war in Ukraine rages and a trade war with China shows little sign of ending.

Washington and Beijing have hiked tariffs on each other’s exports and threatened to cut off trade in critical minerals and technologies altogether.

The White House formally announced the trip on Thursday (US time). Details remain in flux, including the meeting between leaders of the world’s two largest economies.

Neither side expects a breakthrough that would restore terms of trade that existed before Trump’s second-term inauguration in January, according to a person familiar with the conversations.

Instead, talks between the two sides to prepare for the meeting focused on managing disagreements and modest improvements.

An interim agreement could include limited relief on tariffs, an extension of current rates, or China committing to buy US-made soybeans and Boeing aeroplanes.

Beijing reneged on similar promises in a 2020 deal with Trump.

Washington could let more high-end computer chips flow to Beijing, which in turn could loosen controls on rare earth magnets that have angered Trump.

Or, nothing could come of the talks at all.

On Wednesday (US time), US Treasury Secretary Scott Bessent said the Trump-Xi talk would be a “pull-aside”, suggesting nothing formal.

Trump later told reporters the two would have “a pretty long meeting”, allowing them to “work out a lot of our questions and our doubts and our tremendous assets together”.

China has not confirmed a meeting is planned.

Trump is expected at the Association of Southeast Asian Nations summit, which starts on Sunday in Kuala Lumpur, Malaysia.

There, he could oversee the signing of a ceasefire deal between Thailand and Cambodia.

The deal would formalise an agreement that ended the worst fighting in years between the two countries in July, though it’s short of a comprehensive peace deal.

After that stop, Trump will head to Japan to meet Sanae Takaichi, the newly elected prime minister.

Takaichi is expected to affirm plans by her predecessor to hike military spending and to make $US550 billion ($845 billion) in Trump-directed investments in the US.

Then, in Busan, South Korea, Trump plans to meet Xi ahead of an international trade summit.

Trump is set to return to Washington before the Asia-Pacific Economic Co-operation leaders’ forum gets under way, according to the schedule announced by the White House on Thursday.

Trump has threatened to raise tariffs on Chinese imports to a total of some 155 per cent from November 1 if they cannot strike a deal. That would almost certainly provoke a reaction from Beijing and end a truce that paused tit-for-tat hikes.

Beyond trade, the two leaders are expected to discuss Taiwan, a long-running US-China irritant, and Russia, a Chinese ally now subject to expanded US sanctions over the war in Ukraine.

Trump is also trying to close trade deals with Malaysia and India, while shoring up a deal that has already been struck with South Korea.

US and South Korean relations have been strained by Seoul’s concerns over the $US350 billion ($538 billion) investment in US companies sought by Trump and the deportations of the country’s foreign workers.

-with AAP