ConocoPhillips, the third-largest U.S. oil company, has agreed to sell its U.S. gasoline stations in Utah and nine other states to PetroSun Fuel for $800 million, to focus on the more profitable businesses of producing and processing petroleum.

The sale includes 600 stations in the 10 states, with annual sales exceeding 1 billion gallons of fuel, PetroSun said Wednesday in a statement. PetroSun is buying stations in Missouri, Kansas, Oklahoma, Texas, New Mexico, Utah, Colorado, California, Oregon and Washington.

Terry Hunt, a spokeswoman for Houston-based ConocoPhillips, confirmed the transaction. The sale must still be approved by regulators.

ConocoPhillips joins its larger U.S. rivals, Exxon Mobil Corp. and Chevron Corp., in selling retail operations to devote more resources to exploration, production and refining, where much more money can be made. Crude oil has surged from $45 per barrel in 2004 to around $120 this past week.

The gas-station sale to PetroSun marks the completion of a plan by ConocoPhillips, announced in December 2006, to sell 830 stations.

"They had offloaded a bunch of stations a while ago, so they had relatively few left," said James Halloran, who helps manage $34 billion in assets, including 1.7 million ConocoPhillips shares, at National City Private Client Group in Cleveland. "The question for Conoco was, do we want to do an upgrade of the filling stations to make them more profitable?"

Major oil companies now own fewer than 5 percent of gas stations, with the rest owned by smaller chains and independent operators.

Closely held PetroSun said it is making the purchase through a newly formed affiliate called Pacific Convenience & Fuel LLC. The stations will operate under the Conoco, Phillips 66 and 76 brands. ConocoPhillips and Tower Energy Group will supply fuel, PetroSun said.

Contributing: Associated Press.