Nicaragua offered today to negotiate the crucial question of arms supplies to El Salvador and a broad range of other major differences it has with Washington in a six-point proposal that the Sandinista leadership said it hoped would "put an end to the excuses" preventing successful regional peace talks.

In a speech here marking the fourth anniversary of the Sandinista overthrow of Anastasio Somoza, government junta coordinator Daniel Ortega told a crowd of more than 50,000 that Nicaragua's revolutionary leftist government also remains ready to negotiate a nonaggression pact with neighboring Honduras, to discuss an "absolute end" to material support for forces opposed to any Central American government and to agree to the prohibition of all foreign military bases in the region.

In what many diplomats regard as a crucial point, the Sandinistas also said they are willing to discuss these issues in multilateral, regional terms despite what Ortega calls their "absolute conviction that the greatest threat to peace in the region demands bilateral solutions."

Previously, Nicaragua had insisted that its problems with Honduras, the home base for anti-Sandinista rebels funded covertly by Washington, were a subject only for separate bilateral talks with Honduras and the United States.

Ortega's speech comes as Nicaragua faces mounting pressure from Washington and its Central American allies. Washington has justified funding the rebels by accusing Nicaragua of providing crucial material support to leftist rebels fighting the Salvadoran government. With increasingly harsh rhetoric the Reagan administration has sought to portray Nicaragua as a base for "Soviet-Cuban" aggression in the region.

In a pointed speech yesterday seeking to bolster domestic support for his anti-Sandinista policies, President Reagan said flatly, "The Soviets and the Cubans are operating from a base called Nicaragua. And this is the first real communist aggression on the American mainland."

Besides the call for a pact with Honduras, the Nicaraguan proposal listed "a total halt to the supply of arms by any nation to the conflicting forces in El Salvador." This presumably would include U.S. support to that government as well as Nicaraguan support to to the guerrillas.

It called for discussion of a halt to "all military aid in the form of arms supplies, military training, the use of territory, attacks or any other forms of aggression against the opposing forces of any Central American government."

Additionally, it called for an end to "economic discrimination," referring to U.S. restrictions on Nicaraguan exports and opposition to international bank loans to the Sandinistas. It also sought the prohibition of foreign military bases and suspension of military exercises in the region.

Ortega's speech was more moderate than on any of the three earlier anniversaries of the Sandinista-led victory that overthrew the four-decade dictatorship of the Somoza family. U.S. Ambassador Anthony C.E. Quainton walks out of such events almost as a matter of course. Today, he stayed and told reporters afterward that "the overall tone of the speech was not one to have added to the overall problem of our bilateral relations."

But the leadership here clearly is preparing for the possibility of a greatly expanded regional war.

Although the word "conscription" is not in use, Ortega announced what he called "a bill of law for patriotic military service." Specifics of the law have not been announced.

Ortega also announced efforts to answer several basic complaints frequently voiced by Nicaragua's workers and peasants. Many small farmers and members of government cooperatives will be absolved of their debts in a detailed program outlined by Ortega today. Ortega also said that while land reform here has eliminated the power of a small elite that once dominated 42 percent of the best farms, "the revolution guarantees the ownership of land to those who work it."

Although today's speech marks the first public acceptance of handling Nicaragua's problems with Honduras in a regional context, the Sandinistas previously have indicated a willingness to discuss El Salvador. Additionally, today's proposal echoed many negotiating points that have been endorsed by Washington during the past 15 months.

The basic position of Washington, Costa Rica, Honduras and El Salvador has been that Nicaraguan support for revolutionary movements outside its borders cannot be tolerated and must be dealt with in a complex regional context.

Ortega's proposal came two days after the presidents of Mexico, Venezuela, Colombia and Panama met in an attempt to revive the stalled "Contadora initiative" aimed at providing a forum for regional talks.

The foreign ministers of five Central American nations were scheduled to gather late today in Guatemala City to discuss the Contadora meeting, although the presence of Nicaraguan Foreign Minister Miguel D'Escoto was doubtful because of today's events here.

Ortega described the proposals as an effort to take advantage of whatever momentum toward talks was begun in the Contadora meeting.

Ortega also said that he hoped the United Nations Security Council would act to "supervise and guarantee compliance by all countries" with whatever accord might be reached.

Ortega did not comment on the naming of former secretary of state Henry A. Kissinger to head a bipartisan commission appointed by the president to reexamine Washington's Central American policy.

But the often acerbic official Sandinista paper Barricada noted in a front-page headline that "Reagan has thrown the man who killed Allende at us," in a reference to Kissinger's role in U.S. support for the overthrow of then-Chilean Communist president Salvador Allende.