SAN SALVADOR, OCT. 8 -- A plan by more than 4,000 Salvadoran refugees in Honduras to return en masse to their home villages has put the government of President Jose Napoleon Duarte in a political bind and raised the prospect of a confrontation at the border.

As many as 4,500 Salvadoran refugees living at the Mesa Grande camp in southwestern Honduras have declared their intention to cross into El Salvador Saturday in order to return to five villages that have been the scenes of conflict between the Army and leftist guerrillas. A delegation of foreign supporters, including 10 American members of church groups, plans to try to accompany the refugees despite opposition from the Duarte government.

The government and the military see the return as part of a plan by the Marxist-led rebels of the Farabundo Marti National Liberation Front to rebuild popular support and logistics bases in a strategic corridor leading from guerrilla strongholds in Chalatenango province to the Guazapa volcano north of the Salvadoran capital.

However, foreign analysts say, a government decision to bar the refugees from returning to El Salvador would carry a high political cost because of Duarte's frequently stated position that democracy has been restored here and that rebels and exiles should come back to join the political process.

"This is an action against the law of the country," Duarte said of the Americans' plan to accompany the refugees. "We do not permit any foreigner to get involved in national problems." He said that if the refugees have documents to prove that they are Salvadorans from the villages in question, they will be allowed to return. But in any case, he added, no foreigners would be allowed to cross the border with them.

"What the guerrillas need is population to protect them, give them information and demand things of the government," Duarte told a news conference last night in explaining what he sees as the rationale behind the plan.

In an indication of the government's concern, a delegation traveled to the Mesa Grande camp today to try to persuade the refugees to delay their return.

According to American and Salvadoran backers of the refugees' plan, Duarte's insistence on documentation is intended simply to block their return. Oscar Ramon Rosales Melendez, a spokesman for the National Committee for Repopulation, a leftist Salvadoran group helping to organize the repatriation, said the military wants the refugees to come back individually or in small groups so that it can continue a practice of interrogating them before resettlement.

Jean Stokan, a spokeswoman for Going Home, an American church organization formed in May to aid the repatriation of Salvadoran refugees, denied that the participation of American church activists would violate a Salvadoran law against foreigners' involvement in political demonstrations here. She said by telephone from Washington that the 10-member delegation with the refugees in Mesa Grande camp is led by Lutheran Bishop Gustav Schultz of San Francisco and includes representatives of the National Council of Churches, the Chicago Religious Task Force and other church groups.

If the repatriation plan went ahead, it would be the largest single group of war refugees to return to El Salvador since fighting broke out between the FMLN and the Salvadoran armed forces in 1979.

According to the office of the U.N. High Commissioner for Refugees, nearly 20,700 Salvadorans live in refugee camps in Honduras, including 10,500 in Mesa Grande.

Of the Mesa Grande camp's population, about 40 percent want to go home and have written to the U.N. refugee office to ask for assistance and to pass on eight demands to the Salvadoran government, a U.N. spokesman said.

Among the demands are three that have been rejected by the Salvadoran government: no military presence in the resettled areas, no forming of civil defense units and no forced recruitment into the Army, which is the Salvadoran method of enforcing mandatory national service.

Many of the Mesa Grande refugees are survivors of massacres in which hundreds of villagers were killed by the military in 1980, and they harbor strong resentments against the Salvadoran Army, refugee officials said.

"These are people with sympathies that lie more with the FMLN," a U.S. church source here acknowledged.