President Trump on Friday cleared the way for Japan-based Nippon Steel to potentially acquire U.S. Steel, though details about the structure of the deal — including a possible "golden share" held by the federal government — remain unclear. 

The president signed an that says Nippon can buy the iconic Pittsburgh-based steelmaker as long as both parties sign a "national security agreement."

The two companies  Friday that they agreed to the terms of the government's national security agreement, which they said mandates $11 billion in new investments by 2028 and provides for "a Golden Share to be issued to the U.S. Government."

Nippon and U.S. Steel said they expect the deal — referred to as a partnership — to be "finalized promptly." They thanked Mr. Trump, saying they "look forward to putting our commitments into action to make American steelmaking and manufacturing great again." 

Some details about the Nippon-U.S. Steel partnership are not clear. Mr. Trump said earlier this week that the government's golden share would give the United States "51% ownership" and "total control" over U.S. Steel, but Japanese news outlet Nikkei Asia an unnamed Nippon executive who said the company needs "management freedom" over the combined company.

Mr. Trump announced he would allow a "partnership" between Nippon and U.S. Steel last month.

The deal between Nippon and U.S. Steel has faced tumult and uncertainty since a nearly $15 billion merger was first proposed in late 2023. Former President Joe Biden rejected the deal on national security grounds in the waning weeks of his time in office, but Mr. Trump ordered a new review of the deal and suggested Nippon could agree to "invest heavily" in U.S. Steel's facilities rather than fully acquiring the company.

U.S. Steel has said the Nippon deal will allow for new investments in the company's aging facilities, including its Mon Valley Works in the Pittsburgh area. If the deal isn't approved, U.S. Steel has warned it may need to move its headquarters away from Pittsburgh and focus on cheaper ways of making steel than Mon Valley's blast furnaces, putting scores of jobs into jeopardy.

But the United Steelworkers union is staunchly opposed to the deal, calling Nippon's promises to invest in steel mills "public relations" and accusing the company of job-costing unfair trade practices.

Rival steelmaker Cleveland Cliffs — whose offer to buy U.S. Steel was — has also blasted the deal, accusing Nippon of dumping cheap steel in American markets and saying U.S. Steel "rejected an all-American solution and insisted on pursuing a doomed-to-fail cash out sale." In a lawsuit against the government in the waning days of the Biden administration, Nippon and U.S. Steel accused Cleveland Cliffs and the steel union of . 

Meanwhile, Mr. Trump doubled tariffs on foreign steel imports last month.