US stock markets tumbled on Thursday as investors parsed the sweeping change in global trading following Donald Trump’s announcement of a barrage of tariffs on the country’s trading partners.

All three major US stock markets closed down in their worst day since June 2020, during the Covid pandemic. The tech-heavy Nasdaq fell 6%, while the S&P 500 and the Dow dropped 4.8% and 3.9%, respectively. Apple and Nvidia, two of the US’s largest companies by market value, had lost a combined $470bn in value by midday.

Meanwhile, the US dollar hit a six-month low, going down at least 2.2% on Thursday morning compared with other major currencies and oil prices sank on fears of a global slowdown.

Though the US stock market has been used to tumultuous mornings over the last few weeks, US stock futures – an indication of the market’s likely direction – had plummeted after the announcement. Hours later, Japan’s Nikkei index slumped to an eight-month low and was followed by falls in stock markets in London and across Europe.

The White House drafted up a list of countries, including some of its largest trade partners and ones uninhabited by humans, that will be receiving reciprocal tariffs. Many economies will see new tariffs above 20%, including the EU, China, Japan and Taiwan.

The 10% baseline tariff will go into effect on 5 April, while the reciprocal tariffs will begin on 9 April, according to the White House.

“The markets are going to boom,” Trump told reporters at the White House as he left for Florida for the weekend. “I think it’s going very well.”

Economists have for months warned that high tariffs are a major risk to the US economy, pushing prices up for consumers on everything from cars to wine along with destabilizing the US’s role in the global economy.

But that didn’t stop Trump from taking a celebratory tone at the event he dubbed “liberation day”. Trump tried to paint the tariffs as the start of “the golden age of America”.

“We are going to start being smart and we’re going to start being very wealthy again,” Trump said.

On Thursday Howard Lutnick, the commerce secretary, defended the move. “The president is not going to back off what he announced yesterday. He is not going to back off,” he told CNN.

Multiple major American business groups have spoken out against the tariffs, including the Business Roundtable, a consortium of leaders of major US companies including JP Morgan, Apple and IBM, which called on the White House to “swiftly reach agreements” and remove the tariffs.

“Universal tariffs ranging from 10-50% run the risk of causing major harm to American manufacturers, workers, families and exporters,” the Business Roundtable said in a statement. “Damage to the US economy will increase the longer the tariffs are in place and may be exacerbated by retaliatory measures.”

In a statement, the National Retail Federation, a lobbying group for the retail industry, said that the new tariffs negatively affect the business environment for retailers.

“More tariffs equal more anxiety and uncertainty for American businesses and consumers. While leaders in Washington may not care about higher prices, hardworking American families do,” the group said.

Contrary to what Trump has said about the jobs the tariffs will create, the National Association of Manufacturers said that tariffs actually “threaten investment, jobs, supply chains and, in turn, America’s ability to outcompete other nations and lead as the preeminent manufacturing superpower”.

The tariffs also appear unpopular among voters. A poll released on Wednesday ahead of Trump’s announcement found that just 28% of Americans believe tariffs help the economy, while 58% believe the impacts will be damaging.

But in his speech yesterday, Trump appeared ready to be defiant against any criticism.

“In the coming days, there will be complaints from the globalists and the outsources and special interests and the fake news,” he said. “This will be an entirely different country in a short period of time. It’ll be something the whole world will be talking about.”