WASHINGTON (AP) — President Joe Biden has blocked the nearly $15 billion proposed deal for Nippon Steel of Japan to purchase Pittsburgh-based U.S. Steel — affirming his earlier vow on the presidential campaign trail to prevent the acquisition of Steeltown USA’s most storied steel company.

The proposed deal kicked up an election year political maelstrom across America’s industrial heartland and blocking it drew a threat of litigation from Nippon Steel.

“We need major U.S. companies representing the major share of US steelmaking capacity to keep leading the fight on behalf of America’s national interests,” Biden said in a Friday morning statement.

Nippon Steel and U.S. Steel blasted the decision, saying in a joint statement that Biden’s blocking the deal “reflects a clear violation of due process and the law” in a process it said was “manipulated” to advance Biden’s political agenda.

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It also insisted that Biden cited no credible evidence of the deal presenting a national security problem and suggested it will sue, saying “we are left with no choice but to take all appropriate action to protect our legal rights.”

Biden’s decision comes after the Committee on Foreign Investment in the United States, known as CFIUS, failed to reach consensus on the possible national security risks of the deal last month, and sent a long-awaited report on the merger to Biden. He had 15 days to reach a final decision.