The Sandinista government proposed on Thursday that the two-month cease-fire be extended by 30 days to allow negotiators to work out an enduring peace with rebels, but the rebels immediately said no. Azucena Ferrey, spokeswoman for the rebels, known as the Contras, said the Sandinista proposal ``shows they lack good will.'' She noted in a telephone interview that the current cease-fire expires at the end of May, and said that ``if they want to extend it (the cease-fire) they can propose it then.'' Gen. Humberto Ortega, the defense minister and the leader of the leftist government's delegation to the peace talks, told reporters such an extension ``will help improve the conditions under which the negotiations are taking place so that an overall agreement can be discussed to reach a final accord.'' The 60-day provisional truce, which started April 1, is part of an agreement reached by the U.S.-backed rebels and the Sandinistas at the southern border post of Sapoa on March 23. During the truce the two sides are to attempt to negotiate an end to the 6{-year-old conflict that has cost more than 26,000 lives, by government estimates. Ortega, the brother of President Daniel Ortega, announced the offer shortly before the delegations resumed high-level political talks. The government also offered Thursday to let the International Red Cross administer humanitarian aid immediately to the Contras even before rebel combatants gather inside safe zones established during previous talks. The Sandinista proposal was read by Deputy Foreign Minister Victor Hugo Tinoco, who said the offer was ``an attempt to facilitate the pacification process.'' Sandinista and Contra negotiators previously agreed upon seven safe zones in which the Contra fighters are to collect. The two sides differed over operational conditions inside the zones, however, and the rebels have yet to gather inside them. The three-day negotiating session marks only the second time the two sides have met in Managua since the war began in 1981. Recent reports have said that the Contra leadership is divided, with the rebel military commanders opposing any immediate agreement with the Sandinistas. President Ortega on Wednesday predicted an agreement can be reached if both sides bargain in good faith. However, the Sandinistas and the Contras remain far apart on essential issues. Humberto Ortega accused the rebel commanders of taking part in the talks ``not with the purpose of reaching agreement'' but to buy time. American and other sources, speaking on condition of anonymity, said rebel leader Adolfo Calero tried unsuccessfully to oust the top rebel military commander, Enrique Bermudez, a week ago. A U.S. official said the Contra directors split 2-2 with one abstention on whether to remove Bermudez. He ostensibly takes orders from the five-member civilian directorate but believes he should have more influence over rebel decisions, the sources said. Calero argues that civilian control over the movement is essential and sees Bermudez as a threat to that objective. In an effort to dispel rumors of disunity, Bermudez and other Contra leaders issued a statement in Miami on Wednesday declaring support for the talks. Calero, in a telephone interview Thursday, denied there was any split in rebel ranks. ``There are obviously sectors who would be interested in there being such a split,'' he said.