U.S. President-elect Donald Trump on Monday said he would "block" a planned takeover of U.S. Steel by Japanese company Nippon Steel, a deal worth $14.9 billion including debts.

"I am totally against the once great and powerful U.S. Steel being bought by a foreign company, in this case Nippon Steel of Japan," Trump wrote on his Truth Social platform.

"Through a series of Tax Incentives and Tariffs, we will make U.S. Steel Strong and Great Again, and it will happen FAST! As President, I will block this deal from happening."