The president has earned a reputation for bluffing on tariffs. But he has steadily and dramatically raised U.S. tariffs, transforming global trade.

Vietnam’s leadership was caught off guard by US President Donald Trump’s announcement last week that it agreed to a 20% tariff, and the Southeast Asian nation is still seeking to lower the rate, according to people familiar with the matter.

Vietnam, whose exports to the U.S. reportedly comprised 30% of its gross domestic product last year, is especially vulnerable to Trump’s tariffs.