The fresh action would stack on an already steep US rate taking effect Wednesday, the White House told AFP, bringing the total figure to a prohibitive level.

"If China does not withdraw its 34 percent increase above their already long term trading abuses by tomorrow, April 8th, 2025, the United States will impose ADDITIONAL Tariffs on China of 50 percent, effective April 9th," Trump said in a Truth Social post.

As part of a broader plan to impose "reciprocal" tariffs on countries with which the United States has large trade deficits, Trump last week unveiled a 34 percent additional tariff on China, taking effect Wednesday.

Beijing's counter tariff matches Washington's figure, and is set to kick in on April 10. These will stack on existing Chinese duties too.

The world's second biggest economy has also issued other countermeasures, including export controls on rare earth elements.

Since returning to the presidency, Trump has imposed 20 percent added duties on Chinese imports over Beijing's alleged role in the fentanyl supply chain.

With the incoming 34 percent rate and new 50 percent threat, the total additional rate this year could hit 104 percent, the White House told AFP.

The White House added that this new rate piles on existing tariffs from Trump's first presidency, which former president Joe Biden largely kept in place and added to in targeted sectors.

Trump took aim at Beijing's economic practices on social media Monday, criticizing its "non-monetary tariffs" and "illegal subsidization of companies."

He added that "all talks with China concerning their requested meetings with us will be terminated."

But "negotiations with other countries, which have also requested meetings, will begin taking place immediately," Trump wrote on his Truth Social platform.