A gas explosion on the Deepwater Horizon oil rig in the Gulf of Mexico last year killed 11 workers and resulted in one of the worst oil spills in history. A U.S. government investigation into the accident found BP, Transocean and Halliburton committed a series of regulatory violations.
BP sued Transocean for at least $40 billion because it claimed failures at the rig were Transocean's fault.
But BP, in its contract with Transocean, agreed to protect the drilling contractor from "all claims … without limit," the Financial Times reports.
Transocean said it accepts responsibility for some of the costs but blames most of the problems related to the spill on BP.
BP argues Transocean wouldn't be protected by U.S. law if it "materially breached the contract."
The Financial Times notes the case could appear before a New Orleans court in February.