The onetime dynamo is fighting to revive a takeover by Nippon Steel. Other tie-ups could also face obstacles, and going it alone could force cutbacks.

The Japanese firm’s planned purchase of its U.S. rival was blocked last week by President Joe Biden after a year of diplomatic tension, political debate and lobbying efforts from the companies and unions. Biden, who had previously said he opposed the tie-up, cited national-security risks, despite Japan being a close ally.

U.S. Treasury Secretary Janet Yellen said on Wednesday that Nippon Steel's planned acquisition of U.S. Steel received a "thorough analysis" by an interagency review body that was sent to President Joe Biden,