Trump uses tariffs as a key tool to force changes to U.S. trade relationships, but his on-again-off-again approach has roiled markets and stoked uncertainty.

President Donald Trump said at least seven countries can expect tariff letters on Wednesday morning, as he ramped up pressure on nations to strike deals with the United States by saying his new August 1 deadline would not be extended.

The Yale Budget Lab noted that the letters sent Monday would hike the effective tariff rate on U.S. consumers to the highest since 1934.