Molchanov predicted that now that BP has resolved the criminal part of the case, the company has more flexibility in negotiating a settlement to the civil claims.

"BP should be able to take its time with the civil discussions and may be inclined to be somewhat more aggressive in holding its ground that there was no gross negligence," he said.

Some Gulf Coast lawmakers joined environmentalists Thursday in pushing for tough civil fines as the federal government now pursues BP on Clean Water Act violations.

"It’s time to move on to the civil side of things and get Gulf Coast residents every cent they deserve," said Sen. Bill Nelson, a Florida Democrat who co-authored the RESTORE Act. That legislation directs the bulk of civil fines from BP directly back to Gulf Coast communities. The law requires money assessed in the civil fines to go toward environmental and economic restoration in the Gulf.

"People need to remember that this is a very rich company that is basically capitalizing on resources that are in the national interest," said Jacqueline Savitz, deputy vice president of the environmental group Oceana.

"They’re our resources as citizens," Savitz said. "These companies come in, they make a lot of money, billions of dollars, capitalizing on those resources. When it happens, I don’t think we should feel guilty about asking them to pay the full figure. As an advocate for the public, why would we let them come in here and take those risks in our backyard and then not expect them to clean up and pay the consequences?"

BP Group chief executive Bob Dudley said the company’s commitment has been to clean up the spill and pay “legitimate claims.” He said the company is preparing to defend itself in court on the remaining claims.

“We are open to settlements, but only on reasonable terms,” he said.

Dudley said the company apologizes and is taking responsibility. “All of us at BP deeply regret the tragic loss of life caused by the Deepwater Horizon accident as well as the impact of the spill on the Gulf coast region,” he said.

Mary Perez of the Biloxi (Miss.) Sun Herald contributed.