Washington DC - US authorities have extended the deadline for Japan's Nippon Steel to abandon its acquisition of its American rival after President Joe Biden blocked the deal, the companies said Sunday.

Biden cited national security concerns as he put a stop to the $14.9-billion sale of US Steel to the Japanese giant.

Accusing the president of "illegal interference," the companies filed a legal review with the US court of appeals.

The administration will now hold off enforcing the order until June 18, Nippon Steel and US Steel said, extending an initial 30-day deadline.

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"We are pleased that CFIUS (the Committee on Foreign Investment in the United States) has granted an extension to June 18, 2025 of the requirement in President Biden's Executive Order that the parties permanently abandon the transaction," the companies said in a joint statement.

"We look forward to completing the transaction, which secures the best future for the American steel industry and all our stakeholders," it added.

While the outgoing president's decision to block the transaction enjoyed bipartisan support at home, it drew sharp criticism from the Japanese government and business community.

Japan's industry minister labeled it "incomprehensible," and Prime Minister Shigeru Ishiba called on Washington to "explain clearly" its rationale.

Japan and the US are each other's top foreign investors.

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"It is important to appropriately deal with the issue while not undermining the big picture of the Japan-US alliance," Foreign Minister Takeshi Iwaya said Sunday.

"I will ask the US side to remove concerns which are spreading in the business community," he said during a television debate.