There’s an unconventional twist in U.S. President Donald Trump’s trade fights this week: He has rolled out what he’s calling a “secondary tariff” on countries that import crude oil or petroleum products from Venezuela.

A U.S. plan to slap tariffs on countries buying sanctioned Venezuelan oil marks an unprecedented, and potentially potent, mixture of punitive economic measures against a geopolitical foe that Washington could replicate against other countries like Russia and Iran,