NEW YORK ( TheStreet) -- BP ( BP - Get Report) will pay the U.S. government $4.5 billion over a span of years to settle criminal claims against the British oil giant resulting from its April 2010 Macondo well oil spill, called the largest manmade environmental disaster in U.S. history.

In addition to what amounts to the largest-ever criminal settlement with federal authorities, BP said it will plead guilty to 11 felony counts and two of its employees will face criminal manslaughter charges for their role in the oil spill in the Gulf of Mexico.

"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," Bob Dudley, BP's chief executive, said in a statement. " We apologize for our role in the accident, and as today's resolution with the U.S. government further reflects, we have accepted responsibility for our actions," he added.

Felony counts relate to misconduct or neglect relating to the loss of 11 lives; one misdemeanor count under the Clean Water Act, and a felony count of obstruction of Congress. The obstruction charge pertains to two BP communications made to a member of Congress during the spill response about flow rate estimates, BP said in a statement, which noted the resolution is subject to U.S. federal court approval.

While the settlement marks an end to BP's criminal liabilities with the U.S. Department of Justice, the oil producer still faces civil claims. Already BP has embarked on a multi-year plan of asset sales to raise roughly $40 billion to meet civil liability tied to the oil spill.

BP will pay a $4 billion criminal settlement to the Department of Justice in installments over a period of five years, and it will pay the Securities and Exchange Commission a further $525 million, over a period of three years. The company also said it will increase a $38.1 billion provision for spill-related liability by $3.85 billion, as a result of Thursday's settlement. Most legal settlements impact profit on an after-tax basis.

In a statement, BP said it still faces federal civil claims, including a potential violation of the Clean Water Act and other violations of state and federal regulations related to the spill. Analyst estimates indicate that federal civil liability may reach many multiples of the $4.5 billion criminal settlement reached on Thursday.

"BP is prepared to vigorously defend itself against remaining civil claims," the company said. U.S. Attorney General Eric Holder said in a Thursday press conference that federal criminal investigations to the spill continue.

Findings of negligence in BP's drilling in the Gulf of Mexico could lead to billions of further spill liability by the oil giant. An environmental fine associated with gross negligence, if proven, could reach $21 billion, given guidlines under the Clean Water Act.

" Our 'base case' expectation regarding Macondo litigation remains that BP will agree a settlement with the DoJ, which we estimate in the order of ~$20bn," wrote Morgan Stanley analysts led by Martijn Rats, in a late October note to clients.

There was little movement in BP shares in reaction to its criminal settlement, indicating that investors feel comfortable in the capital the oil giant's raised to meet spill related liabilities. Shares in BP were up less than 1% to $40.30 in Thursday trading. Pfizer's ( PFE) $1.3 billion criminal settlement for its marketing of an arthritis drug was the largest fine, prior to Thursday's settlement.

Year-to-date, BP shares are off over 5%. In third quarter earnings, the company raised its dividend 13% to 52 cents, giving it an over 5% annual dividend yield.

In October, BP cut its biggest-ever asset sale divesting a 50% stake in TNK-BP, a Russian oil and gas venture that amounted to 29% of it's the company's daily 2011 oil and gas production, and 27% of its energy resources, tilted towards oil.

Throughout 2012, BP's been doing heavy lifting selling refineries, pipelines and oil fields it sees as not crucial to the company's future, in an effort to sell down a forecast $38 billion in assets by 2013. Were the $12.3 billion in TNK-BP cash to be considered part of that asset sale figure, BP would already be complete on its M&A goals.

In September, BP announced a deal to sell $5.5 billion in Gulf of Mexico oil drilling assets to Plains Exploration and Production ( PXP). The assets being shopped already produce roughly 59,500 barrels a day and hold a reported 120 million barrels of oil in production reserves.

BP had sold over $24 billion in midstream assets, and $10 billion in oil exploration and production assets, according to data compiled by Bloomberg through the end of 2011.

In mid-August, BP said it would sell its California oil refinery and 800 statewide gas stations to refining giant Tesoro ( TSO) for $2.5 billion.

Even with spill-related asset sales hitting a peak in 2012, BP faces substantial risk when it comes to the lingering legal issues from Macondo, both on government charges and civil ones stemming from the Environmental Protection Agency and local communities impacted by the spill.

In a statement, BP said it continues to face an array of federal, state and private civil claims that were not covered in Thursday's settlement.

"A further announcement will be made if and when final agreements are reached. Until final agreements are reached, there can be no certainty any such resolutions will be entered into," said the company on Thursday.

BP has already spent more than $14 billion in spill cleanup costs, an allocation agreed just months after the 2010 disaster. The company has also created a $20 billion fund to pay spill claims and civil settlements, of which $9 billion has already been paid out, according to a statement by BP.

-- Written by Antoine Gara in New York