The US has hit back at 5 members of the World Trade Organization for retaliating against Washington's import tariffs on steel and aluminum.
China, the European Union, Canada, Mexico and Turkey have all responded to the US levies with tariffs of their own on American products.
The Office of the US Trade Representative said on Monday that such action is without justification and will be challenged at the WTO.
US Trade Representative Robert Lighthizer said the actions taken by President Trump are legitimate and justified under US law and international trade rules.
He added the US will take all necessary actions to protect its interests.
China and some other countries have filed complaints with the WTO over the US steel tariffs.
