US President Donald Trump dramatically increased pressure on China to reach a trade deal by announcing he will hike tariffs on $US200 billion ($A285 billion) worth of Chinese goods this week and target hundreds of billions more soon.
The announcement via Twitter marks a major shift in tone from Trump, who has cited good progress in the talks and praised his relationship with Chinese President Xi Jinping.
China Vice Premier Liu He will still travel to the United States this week for trade talks but shorten his trip, South China Morning Post reported on Monday, citing an unnamed source briefed on the latest plans.
The Wall Street Journal reported earlier that China was considering cancelling this week's trade talks in light of Trump's comments on tariffs.
Any sign of an escalation in the months-long trade war is almost sure to roil financial markets, which have reacted sensitively to developments in the talks between the world's two largest economies.
Trump's announcement comes ahead of another round of talks between US and Chinese officials in Washington scheduled for this week.
Trump's move is a reversal of his decision in February not to increase tariffs from 10 per cent to 25 per cent on $US200 billion of goods, thanks to progress in the trade talks. That increase will now go into effect on Friday, Trump said in a tweet.
The president also said he would target another $US325 billion of Chinese goods with 25 per cent tariffs "shortly" and he suggested that the measures were not leading to price increases for American consumers.
"The Tariffs paid to the USA have had little impact on product cost, mostly borne by China. The Trade Deal with China continues, but too slowly, as they attempt to renegotiate. No!" Trump said.
Tariffs on Chinese goods are paid to the United States by the companies importing the goods; most of those companies are US-based.
The announcement casts doubt on expectations that China and the United States were closing in on a deal to end a trade war that has slowed global growth and disrupted markets.
Chinese Vice Premier Liu He was due to travel to Washington for talks this week after a round last week in Beijing that Treasury Secretary Steven Mnuchin called "productive."
As recently as Friday, Trump said talks with China were going well.
White House economic adviser Larry Kudlow told Fox News that the president's tweet was a warning to the Chinese.
"The president is, I think, issuing a warning here, that, you know, we bent over backwards earlier, we suspended the 25 per cent tariff to 10 and then we've left it there. That may not be forever if the talks don't work out," he said.
But Michael Pillsbury, an informal trade adviser to Trump and the director for Chinese strategy at the Hudson Institute, said Kudlow's remarks downplayed the president's intent.
"I take the president's tweet at face value," he said.