US trade representative Robert Lighthizer has accused China of backtracking on commitments in trade talks, but insisted a deal on tariffs is still possible.
He said President Trump’s threat to impose new taxes on Chinese exports came after China reneged on promises.
But he said a Chinese delegation was still expected in Washington on Thursday for a further round of talks.
US stocks regained ground after sharp falls earlier.
On Sunday Mr Trump said on Twitter the US would more than double tariffs on $200bn (£152bn) of Chinese goods on Friday and could introduce fresh tariffs.
Speaking to reporters on Monday, Mr Lighthizer said: “Over the course of the last week or so we have seen an erosion in commitments by China. That in our view is unacceptable.”
He said China had tried to substantively change the text of an agreement between the countries as it was nearing its final stages.
“We’re not breaking off talks at this point. But for now… come Friday there will be tariffs in place,” Mr Lighthizer said.
Earlier, world stock markets sank following the president’s tweets, with the Shanghai Composite tumbling 5.6%.
However in the US the Dow Jones closed down just 0.3%, having slumped 471 points – almost 1.8% – in early trading.
What did Mr Trump say?
On Sunday the US president tweeted that tariffs of 10% on certain goods would rise to 25% on Friday, and $325bn of untaxed goods could face 25% duties “shortly”.
“The Trade Deal with China continues, but too slowly, as they attempt to renegotiate. No!” he tweeted.
He followed that on Monday by tweeting that the US had been “losing” $500bn a year on trade with China. “Sorry, we’re not going to be doing that anymore!” his tweet said.
After imposing duties on billions of dollars worth of one another’s goods last