Nippon Steel and U.S. Steel together filed lawsuits against the U.S. government over U.S. President Joe Biden’s decision to block a proposed merger between the two companies on January 6.

The Committee on Foreign Investment in the United States had been reviewing the acquisition plan for national security concerns since the plan was announced in December 2023.

The committee left the final decision to President Biden at the end of last year. Biden issued an order to halt the plan on January 3.

Nippon Steel said that it will show that Biden ignored the rule of law to gain political favor, and as a result of his influence the CFIUS failed to conduct a good faith regulatory review process with a focus on national security.

The Japanese company also said that the acquisition is “the best path forward to secure the future of U.S. Steel”, and will defend its rights to achieve its objective.