BP will battle to hold down fines that could hit $18 billion (11 billion pounds) in a new phase of the Gulf of Mexico trial that will rule on how much oil it spilled in 2010 and judge its efforts to plug its well. Starting on Monday in New Orleans, this second of three phases of a trial determining responsibilities for the worst marine pollution ever seen in the United States, could - in the worst outcome for the British firm - land BP with a bill five times greater than the $3.5 billion it has set aside for fines…Much depends on how the court rules on a dispute between BP and the U.S. government over how many million barrels of oil were actually spilled, and on just how culpable BP was in failing to stop it for 87 days…[Also refers to Halliburton, Transocean]