Mexico is currently seeking self-sufficiency to become an exporter to the US and other nations. Pemex, says the investments would be crucial in dealing with rising domestic demand for natural gas. But opponents say proposed new energy contracts violate constitutional sanctions and Mexicans' historical sentiment against foreign involvement in energy.
The opposition believe the danger of a privatization is real and vow to fight a Pemex proposal unveiled this month and supported by the administration of President Vicente Fox.
Although Mexico has become the world's fifth-leading producer of oil, it has fallen behind in developing what are believed to be potentially huge deposits of natural gas.