PITTSBURGH, April 17 (Reuters) - President Joe Biden on Wednesday pledged that U.S. Steel would remain a "totally American company," during remarks to steelworkers at an event in Pittsburgh.

"And that's going to happen, I promise you," Biden told the supportive crowd.

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

United States Steel shares were last down 1.4% at $39.74, paring earlier losses.

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. (Reporting by Steve Holland and Costas Pitas; writing by Susan Heavey and Trevor Hunnicutt; Editing by Caitlin Webber)