Leftist rebels warned Friday they will step up their attacks if President Alfredo Cristiani's rightist government does not return to the negotiating table in good faith.

The warning from the Farabundo Marti National Liberation Front came a day after FMLN guerrillas attacked a second major hydroelectric dam in the north, forcing the government to further ration electricity.Four government soldiers and two guerrillas were killed and five soldiers were wounded in Thursday's predawn attack on the Nov. 5 Dam, which is part of the Lempa River hydroelectric system that provides half of El Salvador's electricity.