WASHINGTON/TOKYO >> President Joe Biden officially blocked Nippon Steel’s proposed $14.9 billion purchase of U.S. Steel today, citing national security concerns, dealing a potentially fatal blow to the contentious plan after a year of review. Nippon paid a hefty premium to clinch the deal and made several concessions, including a last-ditch gambit to give the U.S. government veto power over changes to output, but to no avail. In a statement, Nippon and U.S. Steel blasted Biden’s decision, calling it a “clear violation of due process” and a political move, and saying they would “take all appropriate action” to protect their legal rights.