US Steel (NYSE:X) said Monday it is still committed to pursuing a sale to Nippon Steel (OTCPK:NPSCY) (OTCPK:NISTF), saying "our stockholders will not be well served by turning over control of the company to Ancora.

The asset management firm Ancora is challenging Nippon Steel's proposed acquisition of US Steel following its purchase of a 0.18% stake in the American company. Ancora has accused the US Steel board and CEO David Burritt of pushing the $15 billion deal with Nippon Steel due to a potential $100 million windfall they'll receive if the deal closes.

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.