HARRISBURG — Nippon Steel and U.S. Steel said Wednesday they have finalized their “historic partnership,” a deal that gives the U.S. government a say in some matters and comes a year-and-a-half after the Japanese company first proposed its nearly $15 billion buyout of the iconic American steelmaker.

The pursuit by Nippon Steel for the Pittsburgh-based company was buffeted by national security concerns and presidential politics in a premier battleground state, dragging out the transaction for more than a year after U.S. Steel shareholders approved it.

It also forced Nippon Steel to expand the deal, including adding a so-called “golden share” provision that gives the federal government the power to appoint a board member and a say in company decisions that affect domestic steel production and competition with overseas producers.

“Together, Nippon Steel and U.S. Steel will be a world-leading steelmaker, with best-in-class technologies and manufacturing capabilities,” the companies said.

The combined company will become the world’s fourth-largest steelmaker in an industry dominated by the Chinese, and bring what analysts say is Nippon Steel’s top-notch technology to U.S. Steel’s antiquated steelmaking processes, plus a commitment to invest $11 billion to upgrade U.S. Steel facilities.

In exchange, Nippon Steel gets access to a robust U.S. steel market, strengthened in recent years by tariffs under President Donald Trump and former President Joe Biden, analysts say.

Anthony Rapa, a Blank Rome lawyer in Washington who advises firms on trade, operations and investments, said the government’s intervention in the Nippon Steel-U.S. Steel deal is another sign of a trend that the U.S. is increasingly equating economic security with national security.

He doesn’t see the government’s intervention as chilling foreign investment and said a “golden share” mechanism — to the extent it’s used again by the U.S. to ease national security concerns — is likely to emerge only in sensitive and complex cases.

Still, the episode could cause investors to be more strategic in how they approach transactions, Rapa said.

Anil Khurana, executive director of the Baratta Center for Global Business at Georgetown University, said the U.S. government’s interest in the deal is a sign of the growing importance it places on economic competition with China.

“Clearly the definition of what is national security has expanded to included national economic security, which is where I think this comes in,” Khurana said.

Nippon Steel and U.S. Steel did not release a copy of the national security agreement struck with Trump’s administration.

But in a statement Wednesday, the companies said the federal government will have the right to appoint an independent director and get “consent rights” on specific matters.

Those include reductions in Nippon Steel’s capital commitments in the national security agreement; changing U. S. Steel’s name and headquarters; closing or idling U.S. Steel’s plants; transferring production or jobs outside of the U.S.; buying competing businesses in the U.S.; and certain decisions on trade, labor and sourcing outside the U.S.

Nippon Steel announced in December 2023 that it planned to buy the steel producer for $14.9 billion in cash and debt, and committed to keep the U.S. Steel name and Pittsburgh headquarters.

The United Steelworkers union, which represents some U.S. Steel employees, opposed the deal, and Biden and Trump both vowed from the campaign trail to block it.

The United Steelworkers on Wednesday noted that its current labor agreement with U.S. Steel expires in 2026.