In letters so far to 14 countries, including smaller exporters to the United States such as Serbia, Thailand and Tunisia, Trump hinted at opportunities for additional negotiations, even while warning that reprisals would draw a like-for-like response.

Japan and South Korea have until Aug. 1 to agree new trade terms with the U.S., or face 25% “reciprocal” tariffs. The two Asian countries share vulnerabilities that put them in President Trump’s crosshairs,