Nippon Steel and U.S. Steel say they've finalized their “historic partnership,” a year-and-a-half after the Japanese company first proposed its deal to buy the iconic American steelmaker for nearly $15 billion.

Nippon Steel’s $14.9 billion acquisition of US Steel closed on Wednesday, the companies said, confirming an unusual degree of power for the Trump administration after the Japanese company’s 18-month struggle to close the purchase.

U.S. President Donald Trump said on Friday that concerns over national security risks posed by Nippon Steel's $14.9 billion bid for U.S. Steel can be resolved if the companies fulfill certain conditions that his administration has laid out,