French presidential candidate Nicolas Sarkozy has proposed that Europe apply a carbon tax on American imports if Donald Trump pulls the United States out of the Paris climate pact.
More than 100 countries have ratified the Paris global emissions deal, which was inked in December after marathon talks to cap greenhouse gases that cause global warming.
"Donald Trump has said -- we'll see if he keeps this promise -- that he won't respect the conclusions of the Paris climate agreement," Sarkozy said late Sunday on the TF1 television channel.
"Well, I will demand that Europe put in place a carbon tax at its border, a tax of 1-3 percent, for all products coming from the United States, if the United States doesn't apply environmental rules that we are imposing on our companies," he added.
Sarkozy, a frontrunner for the nomination of the centre-right Republicans party, is also in favour of forcing public authorities in Europe to use more products or materials made in Europe.
Europe can no longer be "weak" or "naive", Sarkozy said, even as he defended the idea of the free movement of people and goods.
US president-elect Trump was elected on an overtly protectionist platform, promising to scrap international trade deals and railing against jobs and factories being sent abroad.
Economists fear that moves to protect national markets through tariffs or other barriers risk kicking off a global cycle of measures that would reduce international trade.
UN Secretary-General Ban Ki-moon told AFP last Friday that Trump might reconsider his pledge to cancel the Paris deal, saying it would "create serious problems if anybody wants to undo it."
France's Republicans party will select this month their candidate for next year's presidential election. Ex-prime minster Alain Juppe holds a lead in the polls over Sarkozy, who was president from 2007-2012.