President Donald Trump is altering a deal between United States Steel and Japan’s Nippon Steel. He said Japan’s steel producer would invest in U.S. Steel instead of owning it outright. U.S. Steel stock fell after his comments.

It was unclear what the details of the investment would be, but Trump said he would meet with the head of Nippon Steel next week and he would be involved “to mediate and arbitrate.”

The details remain unclear. President Donald Trump said he would meet with the head of Nippon Steel next week “to mediate and arbitrate.”