12:43 PM EST, 12/03/2024 (MT Newswires) -- President-elect Donald Trump late Monday vowed to block a proposed takeover of United States Steel ( X ) by Japan's Nippon Steel while both companies reiterated their commitment to the deal.

In a post on his social media platform Truth Social, Trump said he was "totally against" US Steel being bought by a foreign company, reiterating comments he made after the deal was announced last December. Shares of US Steel declined 8.3% in midday trade.

"Through a series of tax incentives and tariffs, we will make US Steel strong and great again, and it will happen fast," he wrote. "As president, I will block this deal from happening."

In an emailed statement to MT Newswires, US Steel said the transaction provides "the brightest future for US Steel, our employees and communities, and our customers" and that the deal should be approved on its merits.

"Nippon Steel has committed to preserve US Steel as a US company headquartered in Pennsylvania and to contribute billions of dollars of investment to our mills and communities, securing the future of steelmaking in Pennsylvania and Indiana," the company said.

In a post picked up by Japanese news site Jiji Press on Tuesday, Nippon Steel stressed its readiness to support the US company's growth, as well as strengthen the US' steel industry. The company did not immediately respond to MT Newswires' request for comment.

The United Steelworkers union, which endorsed Kamala Harris in the US presidential election, welcomed Trump's comments, saying the deal would have "serious long-term implications for US economic and national security."

"Our union thanks him for his continuing commitment to American manufacturing and agrees with him that with proper attention, US Steel will flourish well into the future as a domestically owned and operated company," USW International President David McCall said in a Tuesday statement.

Price: 37.67, Change: -3.28, Percent Change: -8.02