NEW ORLEANS — More than five years after the worst offshore oil spill in U.S. history fouled beaches, coated seabirds in thick goo and threatened delicate marshes, BP has agreed to pay a record settlement to affected states in hopes of bringing an end to a legal drama that has cost the company billions.

BP and five coastal states announced a deal Thursday to provide $18.7 billion in new money to the states. The company said the settlement would bring its full obligations to an estimated $53.8 billion.

The Deepwater Horizon disaster killed 11 rig workers and spewed millions of gallons of crude.

Federal and state government officials touted the record-breaking agreement as a historic milestone in the Gulf Coast’s recovery although some environmental groups and local officials indicated BP should have paid even more.

The settlement also provides BP with a valuable return: Many of the payments, to be made over the next 18 years, could be tax-deductible. In addition, the London-based oil giant is freer to embark on new ventures now that it is finally able to provide shareholders with a clearer cost picture.

“This allows us to manage BP as an oil company,” company CEO Bob Dudley said during a conference call. He said BP could launch as many as 20 major new projects by 2020, depending on oil prices.

The Justice Department said Thursday’s agreement would be the largest environmental settlement in U.S. history as well as the largest-ever civil settlement with a single entity. Civil claims by the five Gulf states and the federal government were, by far, the largest unresolved piece of BP’s financial obligations for the spill.