(ANSA) - Rome, September 4 - A US judge on Thursday ruled BP was "grossly negligent" in the lead-up to the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. The ruling could potentially cost BP billions more in compensation payments. New Orleans judge Carl Barbier also found BP subcontractors Transocean and Halliburton "negligent". The 2010 oil spill was the worst in US history, and BP has set aside $43 billion (33 billion euros) to cover fines, legal settlements and clean-up costs. BP said in a statement that it "strongly disagrees" with the ruling and that it would appeal to a higher court.