SAN SALVADOR -- After initially rejecting proposals from Marxist-led rebels on "humanizing" El Salvador's bloody civil war, the government of President Jose Napoleon Duarte has formed a commission to study them.

The government's reconsideration comes amid a nationwide military offensive against the insurgents and signs of strain in the rebels' alliance with leftist politicians.

Under study by the government commission, reportedly made up of seven political and military leaders, is an 18-point proposal issued May 26 by an alliance of the Farabundo Marti National Liberation Front (known as the FMLN), a Marxist grouping of five guerrilla organizations, and the Democratic Revolutionary Front (FDR), a movement headed by leftist political exiles.

Their document calls for the "humanization and the reduction of the economic, social and political impact of the war" and for resuming negotiations on a previous rebel proposal for a "global political solution" to the eight-year-old conflict.

"Obviously, I cannot accept a plan like this," Duarte said May 28 during a provincial tour. He said that if the rebels wanted peace, they should lay down their arms and "join the democratic process."

One reason for the initial rejection, diplomatic sources said, might have been that the proposal tended to undercut a major speech Duarte was to make June 1, on the third anniversary of his inauguration. He announced an amnesty program for as many as 400 of El Salvador's estimated 750 political prisoners, the release for treatment abroad of wounded guerrillas and a package of economic measures.

The rebel plan offers to suspend the use of mines and booby traps, economic sabotage and the execution of spies and informers. It calls on the military to suspend air strikes and the use of long-range mortars and artillery, permit the "free repopulation" of communities that have been relocated and the "free circulation" of people with their provisions, release all political prisoners and eliminate torture and disappearances.

The plan also says that both sides should suspend "all forms of forced recruitment" and calls on the government to repeal certain taxes, stop rationing electricity and cease psychological warfare.

In addition, the proposal calls for negotiations on the withdrawal of U.S. advisers and for these talks also to deal with a previous rebel demand for establishment of a coalition government including the guerrilla alliance. This has been ruled out by the government, on the basis that it would render illegitimate Duarte's 1984 election. Moreover, the Salvadoran Army has continuously opposed recognition of the rebels as anything more than an outlaw force.

Diplomatic sources say the most attractive points for the government in the rebel proposals -- the offers to suspend the use of mines and economic sabotage -- reflect a recognition by the guerrillas that these actions are highly unpopular and have cost them political support.

While the mining has been militarily effective, it has also caused large numbers of civilian casualties. According to the military's spokesman, Col. Mauricio Hernandez, about 600 soldiers and more than 100 civilians have been wounded by rebel mines this year. Nearly half of civilian mine casualties are children, government statistics report.

"The political cost of sabotage is high for us," acknowledged Jorge Villacorta, a leader of the Democratic Revolutionary Front, in a recent interview in Mexico City. He added, however, that this political cost was compensated by the "military benefit" of economic sabotage, which promotes a "political solution" of the conflict. In offering to suspend such activities, the rebels specifically mentioned transportation stoppages, destruction of electrical facilities and "sabotage of farming for export."

"The proposal has certain positive elements for everyone," said Roberto Viera, the vice minister for communications. "Our objections are that the rebels are trying to generate divisions in our ranks." He indicated that the commission named by Duarte to study the offer would come up with counterproposals. But it appeared unlikely that the government would meet a rebel deadline of July 15 for starting negotiations.

Rebel supporters have indicated that coming up with the proposals caused some strain in the alliance and that there is uneasiness among the more moderate political members over what appears to be, at the same time, new guerrilla strategy on the war front.

"We had a lot of work to do to convince {those in the FMLN} to agree to these proposals," said an underground member of the Revolutionary Democratic Front in an interview here. "This proposal signifies ceding on things that are strategic," such as mining and blowing up electricity pylons, he said.

According to Villacorta, who was agriculture minister from 1979 to 1980, "this is an opportune moment to invest in a political solution." He added, "A military victory of the FMLN is not possible." He said he believed that no U.S. administration -- Republican or Democrat -- would "permit a victory of the FMLN" and that the key for successful dialogue was an American go-ahead on a political solution.

Villacorta and two Revolutionary Democratic Front members in San Salvador separately expressed some reservations about what they see as continued efforts by the leadership of the estimated 6,000 to 8,000 armed rebels to achieve a military victory.

"A military solution will not bring democracy," Villacorta said. "If they {the FMLN} are convinced they can impose a totalitarian government, they will impose it. What prevents that is us."