PITTSBURGH (Reuters) -U.S. Steel and Japanese buyer Nippon Steel said the Pittsburgh-based firm will remain an "iconic American company" even after a planned $14.9 billion takeover, echoing President Joe Biden's promise to local steelworkers.

The two steel giants responded hours after Biden on Wednesday pledged that U.S. Steel would remain a "totally American company," repeating his opposition to the deal.

"And that's going to happen, I promise you," Biden told the supportive crowd during an event in Pittsburgh.

U.S. Steel Corp has agreed to be bought by Nippon Steel for $14.9 billion, but the deal has been described as being on life support since the Democratic president announced his opposition last month.

"The partnership between U.S. Steel and Nippon Steel is the right combination to ensure that U.S. Steel remains an iconic American company for generations to come," the steelmakers said in a joint statement.

"Its iconic name will be unchanged, and its products will remain mined, melted and made in America," the statement said, adding that jobs and plants would be protected.

The partnership would also strengthen the U.S. steel industry's resilience against threats from China and support the "crucial" U.S.-Japan alliance, the companies said.

United States Steel shares closed down 2.9% at $39.13 on Wednesday. Nippon Steel shares were trading up 1.05% at 3,468 yen on Thursday morning in Tokyo.

Biden was in Pittsburgh ahead of November's presidential election, and he used a visit to the headquarters of the United Steelworkers union to push for higher tariffs on Chinese metal imports and new investigations into their trade practices.

A senior administration official briefing reporters ahead of that announcement declined to say whether Biden would use the levers of government to block the deal from going through.

"Nothing new to add," said the official, who declined to be named.

"Let's keep U.S. Steel in America," a woman among the steelworkers shouted to Biden during a meet-and-greet.

"Guaranteed," Biden replied.