French wine producers have typically had a love-love relationship with the United States, their biggest export market. But President Trump’s threat to impose 200 percent tariffs on European wine, Champagne and spirits sent shudders through grand châteaus and small vineyards across the country.

“A 200 percent tax on European wines and spirits would mean an immediate halt to all shipments to the United States,” Gabriel Picard, chairman of the Federation of Wine and Spirits Exporters, told French media on Thursday. “That’s almost 4 billion euros wiped off the French trade balance, for zero gain.”

The size of the tariff suggested by Mr. Trump drew reactions of disbelief. “We are in shock,” said Laurent Delaunay, the president of the Burgundy Interprofessional Wine Bureau, which represents Burgundy winemakers, who added that the tariffs would be “catastrophic” if imposed.

“The United States is our biggest market,” he said. “We have business relations that go back years.”

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