TOKYO (Reuters) - Japan's Nippon Steel said on Thursday it has extended the closing period for its $15 billion purchase of U.S. Steel, expressing confidence that the acquisition will protect and grow the American company.

The estimated closing date was revised to the first quarter of 2025 from the third or fourth quarter of 2024 previously.

On Monday, a U.S. foreign investment committee referred the decision whether to approve or block the deal to U.S. President Joe Biden, who has 15 days to decide.

Biden and his incoming successor, Donald Trump, have both expressed opposition to the purchase.

"Nippon Steel hopes that the President will use this time to conduct a fair and fact-based evaluation of the acquisition. We remain confident that the acquisition will protect and grow U.S. Steel," Nippon Steel said on Thursday.

It added that the review process of the antitrust division of the U.S. Department of Justice was also underway, without specifying when it may end.

(Reporting by Rocky Swift and Katya Golubkova; Editing by Himani Sarkar and Muralikumar Anantharaman)