President Donald Trump has signed a directive to launch a Department of Commerce investigation into whether imports of steel are harming America’s national security.

Wilbur Ross, the secretary of commerce, said on a conference call today that last night the agency began an investigation under Section 232 of the Trade Expansion Act of 1962. Ross said this authorizes him to investigate the effects of any imports into the United States on the security of the country.

“Foreign nations are dumping vast amounts of steel all over the United States which is essentially killing our steel workers and steel companies,” Trump said on the campaign trail. “We will put new American steel into the spine of this country, we’re going to use American steel, we’re going to use American labor, we’re going to come first in all deals.”