President Donald Trump says his tariff announcements slated for Wednesday will amount to a “Liberation Day” for the United States. But American businesses and financial markets are unlikely to be freed from the uncertainty generated by his often stop-and-go trade policy.

The details of the tariffs are still unclear, which is one reason the markets are so on edge. Political leaders are on edge as well, because Mr. Trump has made clear that the tariffs will fall on adversaries like China as well as nations that, until recently, were considered America’s closest defense and intelligence allies.

The Trump administration has been promising since mid-February that it will roll out new tariffs on April 2 — and the big unveil is almost here.