The world's two largest economies have been locked in a fast-moving, high-stakes game of brinkmanship since US President Trump launched a global tariff assault that particularly targeted Chinese imports.

Tit-for-tat exchanges have seen US levies imposed on China rise to 145%, and Beijing setting a retaliatory 125% band on US imports.

The US side had appeared to dial down the pressure slightly on Friday, listing tariff exemptions for smartphones, laptops, semiconductors and other electronic products for which China is a major source.

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But Trump asserted Sunday that there was "no Tariff 'exception'" on those products, saying they remained subject to a 20% rate in "a different Tariff 'bucket.'"

In a post on his Truth Social platform, he said "Nobody is getting off the hook," adding: "We will not be held hostage by other Countries, especially hostile trading Nations like China."

Earlier, Beijing's Commerce Ministry had said Friday's move only "represents a small step" and insisted that the Trump administration should "completely cancel" the whole tariff strategy.

The new exemptions will benefit US tech companies like Nvidia and Dell as well as Apple, which makes iPhones and other premium products in China.

The relief could, however, be short-lived, with some of the exempted consumer electronics targeted for upcoming sector-specific tariffs on goods deemed key to US national defense networks.

Trump has said he will give "very specific" details on Monday, and his commerce secretary, Howard Lutnick, said semiconductor tariffs would likely be in place "in a month or two."

He said pharmaceutical products would "also be outside the reciprocal tariffs," using an administration term for tariffs aimed at bringing all US trade imbalances to zero.