Developing nations in south-east Asia, including wartorn and earthquake-hit Myanmar, and several African nations are among the trading partners facing the highest tariffs set by Donald Trump.

Upending decades of US trade policy and threatening to unleash a global trade war, the US president announced a raft of tariffs on Wednesday that he said were designed to stop the US economy from being “cheated”.

“This is one of the most important days, in my opinion, in American history,” said Trump on Wednesday. “It’s our declaration of economic independence.”

He hailed the moment as “liberation day”, but the tariffs are likely to be met with loud protests from some of the world’s weakest economies. One expert said Trump was likely to be targeting countries that received investment from China, regardless of the situation in that country. Chinese manufacturers have previously relocated to countries such as Vietnam and Cambodia not only due to lower operating costs, but also to avoid tariffs.

The tariffs come as many countries in south-east Asia are already grappling with the fallout from the cuts to USAID, which provides humanitarian assistance to a region vulnerable to natural disasters and support for pro-democracy activists battling repressive regimes.

Cambodia, a developing economy where 17.8% of the population live below the poverty line, according to the Asian Development Bank (ADB), is the worst-hit country in the region with a tariff rate of 49%. More than half of the country’s factories are reportedly Chinese-owned, with the countries exports dominated by garments and footwear.

Next worse-hit is the landlocked south-east Asian nation of Laos, a country heavily bombed by the US during the cold war, with 48%. According to the ADB, Laos has a poverty rate of 18.3%.