The probe, led by Commerce Secretary Wilbur Ross, is expected to determine whether US manufacturers can quickly scale up production during a national security event with their current supply of US and imported steel. The investigation could result in recommendations on whether to curb steel imports.
Speaking in the Oval Office Thursday, Trump characterized the move as another way to bring back manufacturing jobs to the United States, a top priority that he said likely helped him win office.
"For decades America has lost our jobs and our factories to unfair foreign trade," Trump said. "And one steel mill after another has been shut down, abandoned, and closed. And we're going to reverse that."
"Other countries have made a living taking advantage of the United States in so many ways. I've been talking about that for a long time," he added. "As I traveled the country I saw the shuttered factories and the shuttered dreams, and I pledged that I would take action, and I think it's probably one of the primary reasons I'm sitting here today as President. And since the day I entered office, I have followed through on that pledge, big league."
The investigation actually began Wednesday evening, before Trump signed his memo surrounded by representatives of the US steel industry. The document fell under the Trade Expansion Act of 1962, a section of which permits a US president to restrict trade if he determines it is harmful to US security.
The law requires Ross to conduct the administration-wide review within 270 days, though Trump said Thursday he expected the review within 50 days.
Ross explained Thursday the administration wanted to determine whether harsher penalties for excess steel production were required to bolster US security.
"We're groping here to see whether the facts warrant a more comprehensive solution that would deal with a very wide range of steel products and a very wide range of countries," Ross told reporters.
He said his work would focus on whether US production of steel -- currently operating around 70% of capacity -- could quickly scale up to meet the needs of the military.
"One of the factors relating to national security would be if you needed a very rapid buildup, are the skill sets there, particularly are the skill sets there for the very complex alloys that are needed for armor plate and things of that sort," he said.
Trump has railed against China for its excess steel production, but it's unclear whether any potential restrictions on steel imports will fall solely on China following the administration review. Since taking office, Trump has tamped down on his harsh rhetoric about China in an effort to cooperate with Beijing on North Korea.
The US has taken action against China through the World Trade Organization in an attempt to limit its excess production of steel, but Ross said Thursday that route was a "porous system," with a limited set of potential actions and ways for countries to skirt the rules. He said China had increased its steel imports, despite US efforts to reduce its longstanding trade deficit in steel products.
The US imports steel from more than 90 countries, according to the International Trade Administration. Top providers include Canada, Mexico, Russia, Brazil, Turkey and Germany.
Ross said Thursday that imports have increased in the first months of this year.
"In the first couple months of this year alone, steel imports rose 19.6% ... and are now more than 26% of the entire US marketplace," he said. "So it's a very serious impact on the domestic industry."