NEW ORLEANS (AP) -- With billions of dollars at stake, the trial to figure out how much more BP and other companies should pay for the nation's worst offshore oil spill began Monday with the federal government saying the oil giant was mostly to blame for a disaster caused by putting profits ahead of safety.

Justice Department attorney Mike Underhill said BP PLC, which leased the rig and owned the blown-out Macondo well, said the disaster resulted from the London-based company's "culture of corporate recklessness."

"The evidence will show that BP put profits before people, profits before safety and profits before the environment," Underhill said during opening statements.

Eleven workers died when the rig exploded April 20, 2010, and millions of gallons of oil spilled into the Gulf of Mexico. U.S. District Judge Carl Barbier is hearing the case without a jury and - barring a settlement - will decide months from now how much more money BP and other companies involved in the ill-fated drilling project owe for their roles in the environmental catastrophe.

"Despite BP's attempts to shift the blame to other parties," Underhill said, "by far the primary fault for this disaster belongs to BP."

Attorney Jim Roy, who represents individuals and businesses hurt by the spill, said BP executives applied "huge financial pressure" on its drilling managers to "cut costs and rush the job." The project was more than $50 million over budget and behind schedule at the time of the blowout, Roy said.

"BP repeatedly chose speed over safety," Roy said, quoting from a report by an expert who may testify later.

Brad Brian, a lawyer for rig owner Transocean Ltd., said the Swiss-based drilling company had an experienced, well-trained crew on the rig. Brian said the Transocean workers' worst mistake may have been placing too much trust in the BP rig supervisors on the rig.

"And they paid for that trust with their lives," Brian said. "They died not because they weren't trained properly. They died because critical information was withheld from them."

Lawyers for BP and Halliburton, the cement contractor that constructed the cement barrier to prevent oil or gas from flowing up the well, will outline their cases later Monday.

Roy said the spill also resulted from rig owner Transocean Ltd.'s "woeful" safety culture. He said the owner of the Deepwater Horizon rig failed to properly train its crew, calling it a "chronic problem allowed by Transocean management to go uncorrected."

"The work force was not always aware of the hazards they were exposed to," Roy said. "They don't know what they don't know."

Roy also said Halliburton deserved some of the blame for providing BP with a product that was "poorly designed, not properly tested and was unstable."

Underhill heaped blame on BP executives and onshore managers for cost-cutting decisions they made in the months and weeks leading up the disaster. He said the primary "rig-based" cause of the blowout was a botched safety test in which two BP rig supervisors, Robert Kaluza and Donald Vidrine, disregarded abnormally high pressure readings that should have been glaring indications of trouble.

Underhill said Vidrine and Mark Hafle, a BP engineer in Houston, discussed the test results over the phone less than an hour before the explosion but failed to take steps that could have prevented the blast.

"Instead, both men, armed with knowledge that could have saved 11 lives and prevented the Gulf oil spill, did absolutely nothing," Underhill said.

Kaluza and Vidrine have been indicted on federal manslaughter charges. Hafle hasn't been charged with wrongdoing.

BP has said it already has racked up more than $24 billion in spill-related expenses and has estimated it will pay a total of $42 billion to fully resolve its liability for the disaster.

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