WASHINGTON, United States (AFP) — The head of the World Trade Organization on Tuesday called on Washington’s trade partners to “keep a cool head” if Donald Trump ends up back in the White House and makes good on his pledge of imposing a 10 per cent import tariff.

“I hope sincerely that that will not happen,” WTO Director-General Ngozi Okonjo-Iweala said in a speech at the Peterson Institute for International Economics, a Washington think tank.

“And that if something happens, that other members will keep a cool head and not retaliate so we can preserve the world trading system.”

However, she warned that if Trump moves ahead with the new tariffs, tit-for-tat measures from other nations could ensue, resulting in a “free-for-all, which would upend the stability and predictability of trade”.

In an interview with CNBC last month, the 77-year-old Republican presidential nominee called himself “a big believer in tariffs,” adding that the likely rise in prices for American consumers from such a measure would be offset by tax cuts.

“I fully believe in them economically when you’re being taken advantage of by other countries,” Trump said in the interview. “Beyond the economics, it gives you power in dealing with other countries.”

Okonjo-Iweala said if other nations were to follow suit, she would hope for mediation, as otherwise, “everyone will lose”.

“It’s a lose-lose situation. There is no winning. And I hope that will become obvious, so it doesn’t happen.”

During his presidency, Trump imposed customs tariffs, particularly on imports from China, to try to force Beijing to make concessions — a policy which ultimately did not change the trade balance between the world’s two largest economies.

He also slapped tariffs on the European Union, which responded by overtaxing American products.

President Joe Biden, Trump’s successor and rival in the November 2024 election, has calmed relations with European allies, but has maintained pressure on China.