The company which leased the Deepwater Horizon rig to oil giant BP has been fined 1.4 billion US dollars (£860 million) after admitting its role in the Gulf of Mexico disaster.
Swiss-based Transocean pleaded guilty to violating the Clean Water Act after its rig exploded in April 2010, killing 11 workers, and spilling millions of barrels of oil.
The deal with the US Department of Justice comes after BP agreed its own 4.5 billion US dollar (£2.8 billion) settlement with the US authorities in November, over criminal charges relating to the disaster.
The US Department of Justice said Transocean admitted its crew members were "negligent in failing fully to investigate clear indication that the Macondo well was not secure and that oil and gas were flowing into the well".
BP, which has long argued that it was not the only company responsible, said: "In settling, Transocean has acknowledged that it played a significant role and has responsibility for the accident. Transocean is finally starting, more than two-and-a-half years after the accident, to do its part for the Gulf Coast."
Under the terms of the proposed deal, Transocean will pay its fine over five years, and the Department of Justice will not pursue further prosecution of the company.
Assistant attorney general for the US Justice Department's Criminal Division Lanny Breuer said: "Transocean's rig crew accepted the direction of BP well site leaders to proceed in the face of clear danger signs - at a tragic cost to many of them.
"Transocean's agreement to plead guilty to a federal crime, and to pay a total of 1.4 billion US dollars in criminal and civil penalties, appropriately reflects its role in the Deepwater Horizon disaster."
Halliburton, which was responsible for cementing the well, is the only company not to have settled over the disaster.
BP said: "Unfortunately, Halliburton continues to deny its significant role in the accident, including its failure to adequately cement and monitor the well."