The tariffs have also provoked political tension, including retaliation from China, which responded to Trump's move with tariffs on US goods and an anti-monopoly probe of Google, among other measures. The speed with which China filed its complaint with the WTO is an indication of Beijing's readiness for the trade fight.

The World Trade Organization said China submitted a request for consultations with the U.S. on the tariffs. China said the duties are discriminatory.

President Donald Trump's tariffs against China have gone into effect. China has retaliated with tariffs against U.S. oil. Tariffs against Mexico and Canada have paused as negotiations continue.

Trump has also threatened to introduce tariffs - a tax on imports - on goods from Canada and Mexico, but paused these for 30 days after both countries agreed to boost border security. The US president has said tariffs are needed to help the American economy and to "protect" the country from the "major threat of illegal aliens and deadly drugs".

A Republican senator from Iowa is pleading for an exemption for potash if U.S. President Donald Trump triggers a trade war by imposing steep tariffs on Canadian imports.