Quebec Premier Francois Legault said Canada should consider putting export taxes on products such as aluminum to create leverage in negotiations with President Donald Trump’s administration.

The leader of Canada’s second most-populous province said the country should retaliate against the U.S. only if Trump actually implements tariffs against its northern trading partner. The president has threatened to do so in March.

If Trump follows through, “I think we should consider also putting exportation tariffs on products like aluminum where they really need us,” Legault told reporters in Washington. That would drive up costs even more for U.S. manufacturers and builders that use the metal.

Trump signed an executive order this week to put 25% tariffs on all steel and aluminum imports, regardless of where they come from. Canada is the source of more than half of U.S. aluminum imports, according to research from Morgan Stanley, and most of that is produced in Quebec.