HARRISBURG, Pa. (AP) -- President Donald Trump is holding a rally in Pennsylvania on Friday to celebrate a details-to-come deal for Japan-based Nippon Steel to invest in U.S. Steel, which he says will keep the iconic American steelmaker under U.S.-control.

Though Trump initially vowed to block the Japanese steelmaker's bid to buy Pittsburgh-based U.S. Steel, he changed course and announced an agreement last week for what he described as "partial ownership" by Nippon. It's not clear, though, if the deal his administration helped broker has been finalized or how ownership would be structured.

Trump stressed the deal would maintain American control of the storied company, which is seen as both a political symbol and an important matter for the country's supply chain, industries like auto manufacturing and national security.

Trump, who has been eager to strike deals and announce new investments in the U.S. since retaking the White House, is also trying to satisfy voters, including blue-collar workers, who elected him as he called to protect U.S. manufacturing.

U.S. Steel has not publicly communicated any details of a revamped deal to investors. Nippon Steel issued a statement approving of the proposed "partnership" but also has not disclosed terms of the arrangement.

State and federal lawmakers who have been briefed on the matter describe a deal in which Nippon will buy U.S. Steel and spend billions on U.S. Steel facilities in Pennsylvania, Indiana, Alabama, Arkansas and Minnesota. The company would be overseen by an executive suite and board made up mostly of Americans and protected by the U.S. government's veto power in the form of a "golden share."

In the absence of clear details or affirmation from the companies involved, the United Steelworkers union, which has long opposed the deal, this week questioned whether the new arrangement makes "any meaningful change" from the initial proposal.

"Nippon has maintained consistently that it would only invest in U.S. Steel's facilities if it owned the company outright," the union said in a statement. "We've seen nothing in the reporting over the past few days suggesting that Nippon has walked back from this position."

The White House did not offer any new details Thursday. U.S. Steel did not respond to messages seeking information. Nippon Steel also declined to comment.

No matter the terms, the issue has outsized importance for Trump, who last year repeatedly said he would block the deal and foreign ownership of U.S. Steel, as did former President Joe Biden.

Trump promised during the campaign to make the revitalization of American manufacturing a priority of his second term in office. And the fate of U.S. Steel, once the world's largest corporation, could become a political liability in the midterm elections for his Republican Party in the swing state of Pennsylvania and other battleground states dependent on industrial manufacturing.

Trump said Sunday he wouldn't approve the deal if U.S. Steel did not remain under U.S. control and said it will keep its headquarters in Pittsburgh.

In an interview on Fox News Channel on Wednesday, Pennsylvania Republican Rep. Dan Meuser called the arrangement "strictly an investment, a strategic partnership where it's American-owned, American run and remains in America."

However, Meuser said he hadn't seen the deal and added that "it's still being structured."

Pennsylvania Republican Sen. David McCormick came out in favor of the plan, calling it "great" for the domestic steel industry, Pennsylvania, national security and U.S. Steel's employees. A bipartisan group of senators, joined by then-Senate candidate McCormick, had opposed Nippon Steel's initial proposed purchase of U.S. Steel for $14.9 billion after it was announced in late 2023.

In recent days, Trump and other American officials began touting Nippon Steel's new commitment to invest $14 billion on top of its $14.9 billion bid, including building a new electric arc furnace steel mill somewhere in the U.S.

Pennsylvania's other senator, Democrat John Fetterman -- who lives across the street from U.S. Steel's Edgar Thomson Steel Works blast furnace -- didn't explicitly endorse the new proposal. But he said he had helped jam up Nippon Steel's original bid until "Nippon coughed up an extra $14B."

The planned "golden share" for the U.S. amounts to three board members approved by the U.S. government, which will essentially ensure that U.S. Steel can only make decisions that'll be in the best interests of the United States, McCormick said Tuesday on Fox News.

Gov. Josh Shapiro, a Democrat who is seen as a potential presidential candidate, had largely refrained from publicly endorsing a deal but said at a news conference this week that he was "cautiously optimistic" about the arrangement.

In an interview published Thursday in the conservative Washington Examiner, Shapiro said: "The deal has gotten better. The prospects for the future of steelmaking have gotten better."

Chris Kelly, the mayor of West Mifflin, Pennsylvania, where U.S. Steel's Irvin finishing plant is located, said he was "ecstatic" about the deal, though he acknowledged some details were unknown. He said it will save thousands of jobs for his community.

"It's like a reprieve from taking steel out of Pittsburgh," he said.

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Price reported from Washington. AP writer Yuri Kageyama in Tokyo contributed to this report.