Move over Russia, Ukraine and Saudi Arabia. The U.S. looks set to join the group of countries embroiled in disputes at the World Trade Organization involving curbs imposed on national security grounds.

China said it would complain to the WTO about U.S. President Donald Trump's import tariffs on steel and aluminum after failing to win an exclusion, which Washington gave to others such as Canada, Australia and the 28-nation European Union. The U.S. levies stem from probes by Commerce Secretary Wilbur Ross under a little-used part of a Cold War-era American law.

The Geneva-based WTO has never ruled on a dispute involving trade restrictions justified on national security grounds and has never had a case centering on steel and national security. A legal fight over Trump's metal tariffs could shake the global commercial order, according to Robert Zoellick, who served as U.S. trade chief under President George W. Bush.