Nippon Steel has completed its acquisition of U.S. Steel, the companies said on Wednesday, more than a year after it was first announced.

Soon after Nippon announced its plans to acquire U.S. Steel in December 2023, the company, based in Pennsylvania, a swing state in the presidential election, became part of a game of political football. The powerful United Steelworkers union pushed back against the deal, and President Joseph R. Biden blocked it over national security concerns.

Last month, President Trump, who had opposed the deal while he was on the campaign trail, said he had approved a transaction that granted the White House a golden share in the company, giving it extraordinary control over the new company as part of a national security agreement.

Mr. Trump and the companies have frequently referred to the deal as a partnership over the past several weeks, fueling mystery on Wall Street and in Washington over its nature. The companies said on Wednesday that they have “now completed the transaction as contemplated by their merger agreement,” effectively a confirmation that the deal is a sale to Nippon.

Shareholders in U.S. Steel had approved an acquisition that would pay $55 a share in cash if it closed.

“Since announcing our deal, I have engaged in extensive dialogue with many stakeholders, including the employees of U.S. Steel, government officials and community leaders,” Takahiro Mori, the vice chairman of Nippon, said in a statement.