With a court rejecting a federal estimate of the Gulf of Mexico oil spill, BP said it was confident a penalty would be on the low end of what's considered.

Carl Barbier, the judge overseeing the case in the U.S. District Court of the Eastern District of Louisiana, ruled the company released 3.2 million barrels of oil into the Gulf of Mexico in 2010, about 1 million barrels less than the government estimated.

"BP believes that considering all the statutory penalty factors together weighs in favor of a penalty at the lower end of the statutory range," the company said in a late Thursday statement.

Barbier's ruling leaves BP faced with a maximum $13.7 billion fine, down from the maximum $18 billion for violations of the Clean Water Act. The ruling issued Thursday still leaves BP with the largest pollution penalty in U.S. history.

The district court in Louisiana ruled in September that BP's activities at the Macondo well beneath the Deepwater Horizon rig in the Gulf of Mexico amounted to willful misconduct. In its 152-page ruling, the court found a series of BP failures at the well "created the catastrophic situation" that led to the 2010 spill.

The incident left 11 rig workers dead and led to the worst offshore oil spill in U.S. history.

Barbier's latest ruling paves the way to a trial next week in New Orleans that will determine the amount BP will pay, based in part on estimates of as much as $4,300 per barrel released.

A consortium led by the National Wildlife Federation said it was time the British oil company faces justice, nearly five years after the spill.

"BP has dragged out litigation in the courts, challenging every decision only to have each decision against them confirmed by higher courts," they said.

BP said it was reviewing the latest court decision.