Nippon Steel and U.S. Steel filed suits on Monday over President Joe Biden's block of the Japanese giant's proposed acquisition of its American rival, accusing the U.S. administration of "illegal interference" in the huge transaction. 

The companies said in a statement that they jointly filed two lawsuits "to remedy the ongoing illegal interference with Nippon Steel's acquisition of U.S. Steel," accusing Biden of blocking the deal "for purely political reasons."