TOKYO (Reuters) – Nippon Steel and U.S. Steel sent a letter on Sunday to U.S. President Joe Biden about their planned $15 billion merger after media reported that he was preparing to block the deal, a spokesperson for the Japanese steelmaker said.

The spokesperson did not provide details about the letter’s content, but said it was signed by Nippon Steel Chief Executive Eiji Hashimoto and U.S. Steel CEO David Burritt as well as other executives.

U.S. Steel did not immediately respond to a request for comment outside of U.S. business hours. The U.S. embassy in Japan did not immediately have comment.

(Reporting by Yuka Obayashi and John Geddie; Editing by Edwina Gibbs)