US President Donald Trump is threatening to retaliate after French President Emmanuel Macron signed legislation imposing a 3% tax on digital transactions.

"France just put a digital tax on our great American technology companies," Trump tweeted. "If anybody taxes them, it should be their home Country, the USA."

The new French tax isn't specific to American companies, but it is designed to target big companies in general—and the world's big technology companies are disproportionately based in the United States. Companies will need to pay the tax if they generate more than €25 million ($28 million) in French revenue and €750 million ($840 million) worldwide.

In a statement earlier this month, the office of the US Trade Representative argued that the tax "will amount to de facto discrimination against US companies" because the income thresholds are designed to tax big, global—often American—companies while "exempting smaller companies, particularly those that operate only in France."

"We will announce a substantial reciprocal action on Macron’s foolishness shortly," Trump added in his tweet. "I’ve always said American wine is better than French wine!"

An official White House statement made the same point in more diplomatic language.

"The United States is extremely disappointed by France’s decision to adopt a digital-services tax at the expense of US companies and workers," a White House statement said. "France’s unilateral measure appears to target innovative US technology firms that provide services in distinct sectors of the economy."

The White House said that Trump had shared his concerns directly with President Macron during a conversation last week. But France passed the new legislation anyway.

It's not clear what kind of retaliatory measures, if any, the Trump administration will take in the coming days or weeks. In recent months, Trump has been engaged in high-profile trade disputes with China, Mexico, and other countries.