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

Nippon Steel Corp.’s thwarted bid to expand in the US could mean tougher competition for Chinese mills in an already saturated global market.