"On trade, I have decided for purposes of fairness, that I will charge a reciprocal tariff, meaning whatever countries charge the United States of America, we will charge them. No more, no less," Trump told reporters in the Oval Office.
Trump signed a memo ordering his team to start calculating duties to match those other countries charge and to counteract non-tariff barriers such as vehicle safety rules that exclude US autos and value-added taxes that increase their cost.
Thursday's directive stopped short of imposing fresh tariffs, instead kicking off what could be weeks or months of investigation into the levies imposed on US goods by other trading partners and then devising a response.
Targets include China, Japan, South Korea and the European Union. The Republican president's latest round of market-rattling tariffs has ratcheted up fears of a widening global trade war and threatened to accelerate US inflation.
Wall Street - anxious that tariffs may add to inflation and keep the Federal Reserve from cutting interest rates further - breathed a sigh of relief, for the moment, with US stocks adding to the day's gains. A gauge of global stocks touched a record high, and yields on US Treasury securities fell.
Howard Lutnick, Trump's pick for Commerce secretary, said the administration would address each affected country one by one and said studies on the issue would be completed by April 1.
That is also the deadline Trump set on his first day in office for Lutnick and other economic advisers to report to him with plans to reduce the chronic trade imbalances that Trump sees as a US subsidy to other countries.
Trump, who campaigned on a pledge to bring down consumer prices, said prices could go up in the short term as a result of the moves. "Tariffs are great," he said.
A White House official, who spoke to reporters before Trump's event in the Oval Office, said the administration would study countries with the biggest trade surpluses and highest tariff rates first.
Trump's tariffs would match the higher duties charged by other countries, he said, and would aim to counteract burdensome regulations, value-added taxes, government subsidies and exchange rate policies that can erect barriers to the flow of US products to foreign markets.
"They effectively don't let us do business. So we're going to put a number on that that is a fair number. We're able to accurately determine the cost of these non-monetary trade barriers," Trump said.
The broad announcement appeared designed at least in part to trigger talks with other countries.
The White House official said Trump would gladly lower tariffs if other countries lowered theirs. The new tariffs would avoid a "one size fits all" approach for more customised levies, he said, though he did not rule out a flat global tariff.
Trump, who took office on January 20, has already announced tariffs on all steel and aluminum imports beginning on March 12, imposed 10 per cent tariffs on goods from China, and put a 30-day hold on planned tariffs on goods from neighbouring Canada and Mexico.
Trump said on Monday he was also looking at separate tariffs on cars, semiconductors and pharmaceuticals. On Thursday he said car tariffs would be coming soon.
