UPDATE 2-US oil cos, Venezuela not in oil takeover talks yet

(Adds comment from Chevron)

HOUSTON, Feb 13 (Reuters) - Exxon Mobil Corp. (XOM.N) and Chevron Corp. (CVX.N) have not yet started talks with Venezuela over its plan to seize majority control of their multibillion-dollar Orinoco oil projects, top executives from both companies said on Tuesday.

They said they had not yet been briefed on the details of a possible takeover by the OPEC member's government. Exxon Mobil Chief Executive Officer Rex Tillerson said his company may not have time to wrap up negotiations by the government's stated deadline.

Venezuela in early February vowed to strip some of the world's biggest oil companies of their controlling stakes in the heavy oil projects by May 1.

"We have not had conversations about this point regarding the new regime," Tillerson told reporters at a news conference.

"We are waiting on the government representatives to sit down with us and give us some of the details of what exactly is it their objectives are, how you migrate and offer compensation."

Exxon Mobil is partnered with major BP Plc (BP.L) and Venezuelan state oil company PDVSA in the Cerro Negro project, which upgrades extra heavy oil from Venezuela's Orinoco region into synthetic crude for export.

Chevron's Chief Executive David O'Reilly said the company does not yet know the process that any negotiations will take for its own Orinoco project.

"We are aware of the government's desire to increase their ownership in the Orinoco projects. But we don't know much more than that yet until we've entered into some dialogue to understand exactly what the objectives are and what the process will be," said O'Reilly, also speaking at the conference.

"Obviously there will be some negotiations in the coming months," he said.

Oil Minister Rafael Ramirez said on Feb. 1 the state would seize fields operated by foreign companies in the Orinoco region if the deadline were missed, threatening firms such as ConocoPhillips (COP.N), Statoil (STL.OL) and BP in addition to Exxon Mobil and Chevron.

Tillerson said he was unsure if Exxon could wrap up talks with the Venezuelan government before the deadline.

"I don't know enough about it at this point," he said.

Tillerson added that the company's contract for the disputed Natuna gas block in Indonesia was still in force. Indonesia's state oil company, PT Pertamina, has said it wants to double its stake in the project. (Additional reporting by Michael Erman)