British oil company BP announced Monday it has agreed to sell some of its assets in the deep-water U.S. Gulf of Mexico to Plains Exploration and Production Co. for 5.55 billion U.S. dollars.

The move is regarded a big step in BP's drive to cover the cost of its oil well spill in the Gulf two years ago and concentrate investment elsewhere.

BP is selling its interests in three assets: the Marlin hub, Horn Mountain and Holstein. The deal also includes BP's stake in two non-operated assets: Ram Powell and Diana Hoover.

BP said the deal is part of a previously-announced plan to divest the assets and position its Gulf portfolio for long-term growth.

"While these assets no longer fit our business strategy, the Gulf of Mexico remains a key part of BP's global exploration and production portfolio and we intend to continue investing at least 4 billion U.S. dollars there annually over the next decade," said Bob Dudley, BP group chief executive.

"This sale, as with previous divestments, is consistent with our strategy of playing to our strengths as a company and positioning us for long-term growth.

In the Gulf of Mexico that means focusing future investments on our strong set of producing assets and promising exploration prospects," Dudley added.

Under the terms of the agreement, Plains will pay BP a total of 5.55 billion U.S. dollars in cash for the assets. The deal is anticipated to close by the end of 2012.

BP expects to divest assets with a total value of 38 billion U.S. dollars between 2010 and 2013 as it focuses its business around the world on its strengths and opportunities for growth.

With today's agreement, BP has now entered into agreements to sell assets with a value of over 32 billion U.S. dollars since the beginning of 2010.

The divestment is in line with BP's global strategy of playing to its strengths, including the development of giant fields and deepwater exploration, said BP in a statement.

It also reflects a greater focus in the Gulf of Mexico on producing more high-margin barrels from fewer, larger assets.