US Steel and Nippon, whose $14.3 billion merger was blocked by President Joe Biden last week, filed a lawsuit against the US government Monday, claiming Biden’s executive order to bar the companies from combining was signed for “purely political reasons.

The suit, filed in the U.S. Court of Appeals for the District of Columbia, alleges that it was a political decision and violated the companies’ due process.

Growth in the massive U.S. services sector picked-up in December, according to the Institute for Supply Management. Meanwhile, job openings hit a six-month high in November, according to the Labor Department.