Donald Trump and Xi Jinping will put their professed friendship to the test Thursday as the least popular US president in decades and the newly empowered Chinese leader hold tough talks on trade and North Korea.

Trump will be treated to more pomp and ceremony on the second day of his first state visit to China, the crucial stop in his 12-day, five-nation tour of Asia.

The two leaders have stepped up the flattery but the US leader is expected to prod Xi to make more efforts to slash China's massive trade surplus with the United States and curb North Korea's nuclear provocations.

The trip comes as Trump faces the lowest approval ratings for a US president in seven decades, while Xi cemented his status as the most powerful Chinese leader in a generation at a Communist Party congress last month.

Trump praised Xi for his "great political victory" before arriving in Beijing, where the Chinese leader welcomed him with an extensive tour of the Forbidden City on Wednesday.

The grand reception included children exclaiming "welcome to China! I love you!" after a Peking Opera performance at the former imperial palace.

"Emphasising pomp over substance is the Chinese way. With President Trump, they think that the state-visit plus treatment will impress him and buy China some good will," Bonnie Glaser, China expert at the Center for Strategic and International Studies in Washington, told AFP.

Trump was so pleased with the first day of his visit that he used special technology to circumvent China's internet censorship system and post a message to Xi on Twitter, which is banned in the country.

"THANK YOU for the beautiful welcome China! @FLOTUS Melania and I will never forget it!" wrote Trump, who also posted an AFP photo of his visit.

Both leaders say they have struck up a friendship since Trump treated Xi to a plush visit at the billionaire's Mar-a-Lago resort in Florida for their first meeting in April.

But the leaders of the world's top two economies will turn their attention to vexing matters on Thursday.

- 'You cannot support' Pyongyang -

Xi and Trump will oversee a signing ceremony for around $20 billion worth of agreements between Chinese and US companies, a day after $9 billion in deals were already announced.

While the numbers are big, the multi-year deals are a drop in the bucket of the overall trade imbalance, which remained high at $26.6 billion in China's favour in October.

Trump will also seek greater efforts from Xi to restrict trade between China and North Korea, whose economic wellbeing depends on its ties with Beijing.

Though Trump has praised Xi for backing a series of United Nations sanctions, US officials want Chinese authorities to clamp down on unauthorised trade along the North Korean border.

"Without China doing what they need to do we're not going to get to a peaceful solution to this problem," a senior US official said. "Without them really participating lock, stock and barrel in this it's not going to work."

Before arriving in Beijing, Trump used a speech at the South Korean parliament to condemn Pyongyang but also urge China and Russia to fully implement UN sanctions, downgrade diplomatic ties, and sever all trade and technology ties with the North.

"You cannot support, you cannot supply, you cannot accept," Trump said.

He later tweeted a warning to North Korea to avoid "a fatal miscalculation. Do not underestimate us. AND DO NOT TRY US."