Donald Trump has threatened China with an extra tariff of 50% on goods imported into the US if it does not withdraw a countermeasure it announced on Friday.

In a post on his social media platform, Truth Social, the US president said he will introduce the extra tariff unless China withdraws its own 34% counter-tariff on American goods, which it announced on Friday.

Trump originally imposed a tax of 34% on Chinese imports last Wednesday, as he announced tariffs on dozens of US trading partners.

If he does impose the additional 50%, US companies will pay a total rate of 104% on Chinese imports.

In his post on Truth Social, Trump said China had introduced its countermeasure “despite my warning that any country that Retaliates against the U.S. by issuing additional Tariffs… will be immediately met with new and substantially higher Tariffs”.

The escalating tension between the US and China has increased fears of a global trade war. The tariffs would come as a major blow to China’s manufacturers, for whom the US is a key market for exports.

Uncertainty around the tariffs led to a turbulent day on global stock markets.

European markets closed lower after Asian share indexes nosedived, with Hong Kong’s Hang Seng index falling by more than 13%, its biggest one-day fall since 1997.

Trump’s post also indicated that negotiations on countries’ tariff rates “will begin taking place immediately”.

Trump is due to meet Israel’s leader, Benjamin Netanyahu, later today. Tariffs are thought to be among the subjects the two will discuss.

The US president also posted earlier that Japan was sending a negotiation team to discuss tariffs.

And Ursula von der Leyen, the president of the European Commission, offered Trump a “zero-for-zero tariff” deal – although she previously said that she had not ruled out retaliation.

“We are also prepared to respond through countermeasures and defend our interests,” she said.