French Finance Minister Bruno Le Maire urged the U.S. to support a global overhaul of how the digital economy is taxed.

Treasury Secretary Steven Mnuchin has said the U.S. supports the efforts of the Organisation for Economic Co-operation and Development, but he has suggested the first part of the OECD’s plan should be optional. Le Maire said on Sunday that this proposal “won’t work.”

The U.S. needs to show “good faith” in the talks, Le Maire said on France 3 television, calling on Washington to back the plan that’s on the table. If no global deal can be reached, Europe will restart talks on introducing its own tax, he said.

The debate over how to tax big tech companies is heating up, with the U.S. threatening to impose tariffs on about $2.4 billion of French products in retaliation for a new French digital levy. Washington maintains that the tax will discriminate against U.S. companies, including tech giants such as Facebook Inc. and Amazon.com Inc.

Le Maire said the French tax isn’t discriminatory, because it also hits European and Asian companies. Any retaliatory tariffs would have no legal basis, and France is prepared to fight them in the World Trade Organization if necessary, he said.

“This is uselessly aggressive toward France,” Le Maire said.