Nippon Steel Chief Executive Eiji Hashimoto says the top Japanese steelmaker is standing firm on its proposed acquisition and poses no security risks.

TOKYO -- Nippon Steel's plan to buy U.S. Steel has entered a new phase with the companies' declaration of a full-scale legal war against the U.S. government. They hope the lawsuits will overturn President Joe Biden's order to give up the acquisition.

The companies argued in a lawsuit announced on Monday that Biden violated the Constitution by blocking the merger via a sham national security review that deprived the companies of their right to a fair process.

Nippon Steel, whose multibillion-dollar proposal to buy struggling US Steel was blocked by President Joe Biden last week, says it is considering taking legal action against the US government.

U.S. Steel and Japan’s Nippon Steel sued the United States government on Monday in a last-ditch attempt to revive their attempted merger after President Biden blocked it last week on the basis that the transaction posed a threat to national security.

President-elect Trump has also opposed Nippon Steel's $15 billion acquisition of U.S. Steel, which President Biden blocked last week.

President Biden stood next to Gov. Gavin Newsom and pledged full federal support as fires burned through Los Angeles County. President-elect Donald Trump took to social media and blamed 'Newscum.' Mexico’s president has signaled to Donald Trump that she can play the regional renaming game,

Trump opposes U.S. Steel's sale to Nippon, but CEO David Burritt believes he can convince the president-elect that the deal is in the interest of U.S. workers.