The Justice Department is suing to stop Halliburton from merging with rival Baker Hughes.
In the complaint filed today, the feds say the merger would eliminate head-to-head competition, lead to higher prices and weaken innovation in the industry.
The proposed merger is valued at nearly $35 billion, the largest oil field services acquisition ever proposed.
Both companies say they plan to fight the lawsuit.
Federal government sues to stop merger between Halliburton, Baker Hughes