President Joe Biden said Friday that he has decided to block a $15 billion takeover of U.S. Steel by Japanese company Nippon Steel, capping off a yearlong business saga that drifted into election-year politics.

The decision comes after a national security review failed to reach a consensus on the deal and referred the final decision to the president in December. The Treasury Department’s Committee on Foreign Investment in the United States reviews foreign investments in the U.S. to evaluate national security impacts.

Biden faced a challenging political calculus in deciding the fate of the iconic American company: Allow a foreign entity, though one with far greater resources, to assume control of it and put the company on a potentially more sustainable financial footing; or keep it in American hands while risking a greater likelihood that U.S. Steel could go out of business entirely amid intense foreign competition.

"As I have said many times, steel production—and the steel workers who produce it—are the backbone of our nation," Biden said in a statement. "A strong domestically owned and operated steel industry represents an essential national security priority and is critical for resilient supply chains. That is because steel powers our country: our infrastructure, our auto industry, and our defense industrial base. Without domestic steel production and domestic steel workers, our nation is less strong and less secure."

U.S. Steel agreed to be acquired by Nippon in Dec. 2023 for $14.9 billion. It picked the Japanese company over top U.S. steelmaker Cleveland-Cliffs, thinking that a national security review would be less problematic than an antitrust review. But the agreement ran into political opposition from both sides of the aisle. Both Biden and then-candidate Trump pledged to block the deal, even though Japan is a strong U.S. ally. The Committee on Foreign Investment in the U.S., the U.S. government body better known as CFIUS that investigates foreign acquisitions, couldn't reach a consensus and referred the deal to Biden for him to make the call.