Cliffs would purchase all of U.S. Steel for all cash and then sell off the Big River Steel subsidiary to Nucor, sources told CNBC's David Faber. U.S. Steel's headquarters would remain in Pittsburgh under the deal.

Cleveland-Cliffs Inc. is partnering with Nucor Corp. to weigh a potential joint bid for United States Steel Corp., according to a person familiar with the matter. Cliffs’ top boss later confirmed his interest in the American steelmaker at a press event.

U.S. Steel shares rose after CNBC reported that Cleveland-Cliffs is partnering with Nucor for a possible bid to buy U.S. Steel.