The leftist opposition Party of the Democratic Revolution, or PRD, plans to organize a national campaign to protect state-owned oil giant Petroleos Mexicanos, or Pemex, party officials said.

The PRD is "on red alert" in light of government plans for structural reforms at Pemex, party chairman Jesus Zambrano said.

Several governing Institutional Revolutionary Party, or PRI, officials have discussed vague plans for energy industry reforms that threaten state control of Pemex, arguing that it is the only way to modernize the state-owned company, Zambrano said.

PRI officials have made it known in recent days that they are "willing to modify their principles to incorporate the possibility of a private sector role in Pemex, in the energy industry," Zambrano said.

Pemex, the world's No. 4 oil producer with output of about 2.5 million barrels per day, is the biggest contributor to Mexico's Treasury. EFE