BP Plc has accepted a $4 billion payment from Anadarko Petroleum toward the Gulf of Mexico oil spill clean-up, far less than it might have won in court, but a deal that locks its main partner into its share of the blame and any future fines.

While BP has given up around $5 billion in potentially recoupable costs, the deal also removes a vocal and potentially damaging opponent from the field, thereby potentially reduced the final bill for the United States' biggest every offshore oil spill by tens of billions of dollars.

The London-based oil company's shares jumped on the news, to trade up 4.3 percent at 0924 GMT, outperforming a 1.6 percent rise in the STOXX Europe 600 Oil and Gas index.

This is good progress, said one dealer.

BP said on Monday that as part of the deal, Anadarko will no longer pursue its allegations of gross negligence against BP and that the deal excludes possible government fines the parties may have to pay.

As a 25 percent partner in the Macondo well, Anadarko is on the hook for 25 percent of the costs of cleaning up the spill, compensating those affected, and paying government fines.

It could only avoid this responsibility if it proved BP had been grossly negligent -- something which could, potentially, have added around $18 billion to the total amount of fines BP faced.

Fines for leaking oil into U.S. waters are leveled at a level of $1,100 per barrel, or $4,300 if gross negligence is proven. The government has said the Macondo well leaked almost 5 million barrels into the sea.

BP has said the total bill for the oil spill, including government fines, for which it has taken charges of $3.5 billion and research grants of $500 million, will be $42 billion.

This suggests Anadarko could have faced a total bill of up to $9.5 billion.

LESS LIKELY

Investors have priced in a final cost to the company from the spill that is far in excess of BP's estimate. Analysts say deals such as the one announced Monday make the worst-case scenario -- a final bill in excess of $70 billion -- look less likely.

We maintain our view that the ultimate cost to BP could fall ... substantially below the cost inferred by the share price fall since the accident, Richard Griffith, oil analyst at Evolution Securities said.

In May, BP agreed to accept $1.1 billion from the third partner in Macondo, Mitsui & Co., to cover its 10 percent share of cleanup costs.

The company is still suing the companies it hired to help drill the well, Transocean and cement specialist Halliburton, to pay toward the cost of the spill.

Key to forcing Transocean to meet the cleanup bill -- BP has sought the full amount from the drilling contractor -- is convincing a court that Transocean was grossly negligent.

If BP does recoup cash from Transocean or Halliburton, it will pay a portion of this -- up to $1 billion Anadarko under the terms of the deal.

Two lengthy government inquiries have laid the lion's share of the blame for the blowout at BP's door.

The rig blast killed 11 men and caused more than 4 million barrels of oil from the Macondo well to spill into the sea.

(Editing by Hans-Juergen Peters and Andrew Callus)