News Analysis
By Alan Riding, Special To the New York Times
The unexpected resignation last night of Jorge Diaz Serrano as head of Mexico's oil monopoly was the climax to a long and bitter campaign by both Cabinet ministers and outside critics who felt that the company, Petroleos Mexicanos, had become a state within a state. Mr. Diaz Serrano, who was replaced by Julio Rodolfo Moctezuma Cid, a former Finance Minister and long-time associate of President Jose Lopez Portillo, was apparently undermined by his own success. Mr. Diaz Serrano, a 60-year-old former private oil contractor whose post as director-general at Pemex was his first job in government, injected life into the country's lethargic oil bureacracy and, in little more than four years, supervised the tripling of oil production, a rapid ascent in exports and a tenfold rise in Mexico's proven hydrocarbon reserves, to 67 billion barrels. But, as a result, the Government became enormously dependent on oil revenues to maintain the current economic boom, and Mr. Diaz Serrano emerged as one of the country's most influential figures and one of a handful of possible candidates to become the next president.