The deal between US Steel and Nippon Steel includes a national security agreement and $18.3 billion in investments by 2028. Photo / Toru Hanai, Bloomberg via Getty Images

US President Donald Trump signed an executive order today approving a partnership between US Steel and Nippon Steel after the companies reached agreement on US national security guarantees.

The deal brings an end to the long-running saga over foreign ownership of a key national asset that began in December 2023