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.

Separate lawsuits from Nippon Steel and U.S. Steel target President Joe Biden as well as a steelworkers union head and a rival steelmaker’s CEO.

The president said he was moving to protect national security in deciding the fate of the iconic Pennsylvania-based company, which became a contentious political issue in an election year.

U.S. Steel and Nippon Steel said on Monday that it is suing over President Joe Biden's decision to block its sales agreement and a domestic competitor and union over their actions to scuttle the deal.

The companies accuse the president, head of steelworkers union and Cleveland-Cliffs CEO of teaming up to block the transaction.

Nippon Steel is poised to expand its operations in the U.S. and India as it hunts for growth and protection from cheap Chinese exports after its bid for U.S. Steel was blocked by the White House, analysts say.