CARACAS (Bloomberg) — Exxon Mobil Corp., the parent company of Esso, and ConocoPhillips will quit oil and natural-gas projects in Venezuela after the failure of talks with President Hugo Chavez's government, the country's energy minister said.The minister, Rafael Ramirez, confirmed the departures of the companies in signing ceremonies for agreements with four companies that will continue heavy-oil operations in the country. They are Chevron Corp., Statoil ASA, Total SA and BP Plc. The departures of ConocoPhillips and Exxon Mobil were disclosed late yesterday by a person on the government side of negotiations.

Petroleos de Venezuela SA will have stakes of 60 percent to 83 percent in ventures with the four remaining foreign oil producers, Ramirez said. Talks on compensation will be held with ConocoPhillips and Exxon Mobil, he said.

"This is just another step in the complete takeover," said John Parry, an analyst at John S. Herold Inc. in Norwalk, Connecticut. "I think that's why Exxon and ConocoPhillips, who could afford to lose out, are just going to take this to a World Court arbitration."

The companies failed to reach an agreement on remaining in the country after Petroleos de Venezuela unilaterally increased its stakes in heavy-oil projects that can produce about 580,000 barrels of oil a day, a quarter of Venezuela's output.

"Exxon Mobil is disappointed that we have been unable to reach an agreement," spokeswoman Susan Reeves said in an e- mailed statement. "However, we continue discussions with the Venezuelan government on a way forward."

Shares of ConocoPhillips fell $2.24, or 2.9 percent, to $75.80 in New York Stock Exchange composite trading. Shares of Exxon Mobil, based in Irving, Texas, fell 55 cents to $81.82.

With ConocoPhillips leaving, Chevron, the 30 percent owner of the Hamaca heavy oil project, will keep its full stake, Ramirez said. Petroleos de Venezuela will take ConocoPhillips's stake, giving it a 70 percent interest.

The terms are "acceptable," said Ali Moshiri, head of the company's Latin American exploration and production unit.

The projects, the country's largest foreign investment, extract heavy crude from the Faja, a 21,400 square mile) patch of tarry oil that rivals Canada's oil sands in size. The projects, which represent a growing share of production for the world's sixth-largest oil exporter, pump oil and upgrade it so it can be more easily shipped and refined.

Chavez and Petroleos de Venezuela took operational control from the companies that built the plants, including ConocoPhillips and Exxon, on May 1 as part of his quest to create what he calls "21st century socialism". The country also started to take over majority stakes in the projects.

US Energy Secretary Samuel Bodman said he is "concerned" about the departure of the two companies from Venezuela.

"It's not just Venezuela," Bodman said. "We have problems with Nigeria. We have problems with Russia with development of resources."