President Donald Trump revealed his most sweeping economic measure yet Thursday, announcing reciprocal tariffs that could come as soon as this spring, which Trump argues would level the playing field in global trade—though economists project they would increase inflation this year.

The president said his advisers would devise new tariff levels reflecting countries’ tariffs, taxes, subsidies and other policies affecting trade with the United States.

Trump calls it unfair that some countries apply higher tariffs to specific American goods than the U.S. applies back. A new executive order seeks to change that.