U.S. Trade Rep. Jamieson Greer testified before the Senate on Tuesday in a hearing where he defended President Donald Trump’s aggressive trade agenda and massive ramp-up of tariffs.

Stocks have slid since Trump announced extensive 10% tariffs on all imports and, in some cases, higher tariffs based on trade deficits. The tariffs will go into effect at midnight on Wednesday, and Greer fielded questions from Democrats and Republicans.