Washington — President Joe Biden has made good on his months of public opposition to the proposed purchase of American company U.S. Steel by Japan’s Nippon Steel, announcing Friday he is blocking the $14.9 billion takeover. The acquisition would “place one of America’s largest steel producers under foreign control and create risk for our national security and our critical supply chains,” he said in a statement. He did not elaborate on how the deal would jeopardize national security. The collapse of the proposed acquisition represents a victory for workers of the company based in Pittsburgh, Pennsylvania, an electorally crucial swing state.