Ancora Holdings Group, with $10 billion in assets, reported acquiring a 0.18% stake in the Pittsburgh company. It said Monday that U.S. Steel CEO David Burritt and the company’s board have prioritized a sale to Nippon because they stand to receive more than $100 million if it goes forward.

Activist investor Ancora has nominated nine candidates to U.S. Steel's board of directors, as it looks to oust company CEO David Burritt and push the American steelmaker to back out of a $14.9 billion merger deal with Japan's Nippon Steel.

Activist investor Ancora Holdings is preparing to wage a proxy battle at U.S. Steel and wants the company to turn the page from its failed marriage with Nippon Steel, according to people familiar with the matter.