U.S. President Donald Trump threatened on Friday to slap heavy tariffs on French wine in response to taxes on American tech companies just before heading to France for a summit of G7 leaders.

"Those are great American companies, and frankly, I don't want France going out and taxing our companies. Very unfair," he told reporters outside the White House shortly before boarding his helicopter on Friday, local time.

"And if they do that, we'll be taxing their wine or doing something else. We'll be taxing their wine like they've never seen before. That's for us to tax them, not for France to tax them."

It is not the first time that Trump threatened to tax French wine. About a month ago, he told French President Emmanuel Macron that he was concerned about the proposed digital services tax.

The digital tax primarily targets companies that use consumer data to sell online advertising. The tax is designed to stop multinationals from avoiding taxes by setting up headquarters in low-tax European Union countries. Currently, the companies pay nearly no tax in countries where they have significant sales.

Read more: Trump says U.S. could tax French wine in retaliation for digital tax

"If anybody taxes them, it should be their home Country, the USA. We will announce a substantial reciprocal action on Macron's foolishness shortly," Trump tweeted on July 27. "I've always said American wine is better than French wine!"

The French law does not specifically target U.S. companies. It targets any digital company with yearly global sales worth more than 750 million euros (835 million U.S. dollars) and French revenue exceeding 25 million euros (27 million U.S. dollars). The revenue threshold is supposed to allow more room for smaller companies to enter the market.

However, the Trump administration emphasizes that the services covered under the tax are ones in which U.S. firms are global leaders. 

France's new digital services tax "targets U.S. firms almost exclusively and largely spares French companies," said the U.S. Chamber of Commerce.

(With input from Reuters, AFP, and AP)