SAN FRANCISCO (REUTERS) - A judge in the United States ruled on Tuesday that British oil giant BP recovered 810,000 barrels of oil from its 2010 spill site and that this amount should be excluded from certain penalties it may face, cutting its maximum fine by as much as US$3.5 billion (S$4.3 billion).

Just days before he presides over a spill-related civil trial due to start on Feb 25 in New Orleans, US District Judge Carl Barbier deemed those barrels as "collected" during the spill. BP had sought this reduction in the penalty-relevant total more than a month ago.

"The 'Collected Oil' flowed from the subsurface reservoir, through the well, through the blow-out preventer, and never came into contact with any ambient sea water, and was not released to the environment in any way," the ruling said.

Earlier, BP said the US Department of Justice backed its assertion that the oil recovered directly from the leaking Macondo well should not count when it comes to fines that could be levied under the US Clean Water Act. It also repeated that the total 4.9 million spilt barrels estimate made by the US government in its claim against BP, including barrels recovered, was too high by 20 per cent.

The maximum fine payable under the act is US$4,300 per barrel, so a calculation based on 4.9 million barrels spilt would have forced BP to pay as much as US$21 billion under the Clean Water Act, on top of any other fines and penalties, if BP is found guilty of "gross negligence".

Without the gross negligence finding, the fine could be up to US$1,100 per barrel - or US$5.4 billion - so that potential fine was cut by nearly US$900 million with the ruling on Tuesday.

Separately, Judge Barbier signed on Tuesday a US$1 billion civil settlement between the US government and Transocean related to the spill, which had been struck last month. Transocean's Deepwater Horizon rig was destroyed in the blowout.