Senator Brown is joining a growing bipartisan group of senators opposing the acquisition of U.S. Steel by Nippon Steel, which would put the iconic American company under the control of a Japanese competitor.

The senior senator of Ohio said in a statement that he supports U.S. Steel remaining under the control of a pro-union, American company.

“U.S. Steel has a proud tradition of American manufacturing. If U.S. Steel must be sold, I have made clear that a pro-union American company that values its workers — like Cleveland-Cliffs — should buy it,” Mr. Brown said.

He added that a “foreign company should not be able to swoop in, ignore the voices of union workers, and buy a major American steel manufacturer behind closed doors,” and that the acquisition “insulted American steelworkers by refusing to give them a seat at the table.”

Mr. Brown is joining the junior senator of Ohio, Senator Vance, in opposing the acquisition, alongside Senators Fetterman and Hawley.

“It’s absolutely outrageous that they have sold themselves to a foreign nation and a company,” Mr. Fetterman said in a video posted on X Monday. “Steel is always about security as well, too, and I am committed to doing anything I can do from using my platform or my position to block this.”

He added: “I’m going to fight for the steelworkers and their union way of life.”

In a letter to Secretary Yellen Monday, Messrs. Vance and Hawley voiced their concern about an “absence of any security-focused deliberation on U.S. Steel’s part.”

“The transaction was not the product of careful deliberation over stakeholder interests, but rather the result of an auction to maximize shareholder returns,” the senators wrote. 

They also expressed concern that Nippon Steel had been found guilty of “unlawfully dumping flat-rolled steel products into the U.S. market,” and that “its financial interests are tied into those of Japan.”

Once-proud U.S. Steel was founded by J.P. Morgan in 1901 and dominated the steel trade for decades through America’s golden age of manufacturing and union labor, but it has been in steady decline since the 1980s. It is now the third largest American steel manufacturer, behind Nucor and Cleveland Cliffs. All three of these American companies are dwarfed in size by Asian competitors, most of them from Communist China.

The steel market has been the site of some of America’s more recent protectionist trade policies, with President Trump imposing a 25 percent tariff on steel and President Biden keeping those tariffs in place.

“We believe this transaction is in the best interests of our two companies, providing strong, immediate value for U. S. Steel shareholders while enhancing NSC’s long-term growth prospects,” Nippon Steel’s vice president, Takahiro Mori, said in a statement.