The Biden administration's move on Friday to block Nippon Steel's proposed purchase of U.S. Steel raises questions about the once iconic American company's future, with industry sources saying the manufacturer could struggle to energize growth or attract rival acquisition bids.

The president said he was moving to protect national security in deciding the fate of the iconic Pennsylvania-based company, which became a contentious political issue in an election year.

The president says the acquisition could threaten national security. Both steel companies say they will fight the decision.