Key Mexico party seen opposing oil alliances

MEXICO CITY, Feb 28 (Reuters) - A key Mexican opposition party is unlikely to back any oil sector reform proposal that would let private companies form profit-sharing alliances with the state oil company Pemex, a senior lawmaker said.

"For us, risk contracts are unacceptable for now," Sen. Manlio Beltrones told the Mexican daily Reforma.

"Personally, I don't think there's the desired level of consensus," said Beltrones, an influential Institutional Revolutionary Party, or PRI, senator and the party's president in the Senate.

Beltrones, one of the PRI's strongest voices on energy policy, said partnerships with other state-run oil firms would be more acceptable than private sector joint ventures, which opponents say could breach a constitutional ban on companies other than Pemex drilling for Mexican oil.

Mexico is a top U.S. oil supplier but years of underinvestment have left output and reserves declining.

Lawmakers from the three main political parties are trying to draw up an energy bill to give Pemex more autonomy and flexibility, and conservative President Felipe Calderon would also like it to permit private partnerships in specific areas like deepwater oil fields on the U.S. maritime border.

Calderon needs the full backing of the PRI as his party lacks a majority in Congress. Some PRI lawmakers have said they are open to listening to the ruling party's ideas.

The left-wing Party of the Democratic Revolution, however, strongly opposes private investment in the oil sector.

Many oil analysts say strategic joint ventures with experienced foreign firms could speed up Mexico's entry into the crucial but technically challenging deepwater sector. (Reporting by Jason Lange; editing by Jim Marshall)