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…