"These US 'reciprocal tariffs' will inflict serious harm on developing countries, especially the least developed countries, and could even trigger a humanitarian crisis," Wang told WTO chief Ngozi Okonjo-Iweala in a call on Friday, the statement said.

"The United States has continuously introduced tariff measures, bringing enormous uncertainty and instability to the world, causing chaos both internationally and domestically within the US," Wang added.

Beijing said Friday that its 125 percent tariffs on US goods would take effect on Saturday -- almost matching the staggering 145 percent levies imposed by Washington on Chinese goods entering the United States.

But China indicated that it would ignore any further levies by US President Donald Trump because, Beijing said, it no longer makes economic sense for importers to buy from America.

China also said it would file a lawsuit with the WTO over the latest round of levies.

After a week of market mayhem as the world's two largest economies took turns to put up trade barriers, Beijing dismissed Trump's mounting brinkmanship as a "joke" and a "numbers game".

Beijing's retaliation sparked fresh market volatility, with stocks seesawing, gold prices surging and US government bonds under pressure.