BP PLC, Associated Press
In this Monday July 12, 2010 image from video made available by BP PLC, oil flows out of the top of the transition spool, which was placed into the gushing wellhead and will house the new containment cap, at the site of the Deepwater Horizon oil spill in the Gulf of Mexico.

NEW ORLEANS — Lawyers for the government and oil giant BP are preparing for trial in New Orleans that could add more than $13 billion in penalties to the billions BP already has shelled out as a result of 2010 Gulf oil spill.

Federal lawyers say BP should pay as much as $4,300 per barrel spilled after the Deepwater Horizon rig explosion at BP's Macondo well. Based on a court finding that 3.19 barrels polluted the Gulf, the penalties could reach $13.7 billion.

BP will argue for a lower figure in the trial opening Tuesday. It says its costs already have hit $42 billion, including a $14 billion response and cleanup. Its pre-trial briefs say a low-end penalty would accomplish the Clean Water Act's purposes: deterring environmentally dangerous behavior and encouraging effective responses.