Defense Secretary Caspar W. Weinberger yesterday linked the security of the continental United States to the future of El Salvador, speaking of that country as being "on the mainland of the United States."

Defending the mainland ranks "over and above all other pri w0043 ----- r a BC-06/15/83-WEINBE 06-15 0001 Weinberger Links Security of U.S. To the Future Of El Salvador By Joanne Omang Washington Post Staff Writer

Defense Secretary Caspar W. Weinberger yesterday linked the security of the continental United States to the future of El Salvador, speaking of that country as being "on the mainland of the United States."

Defending the mainland ranks "over and above all other priorities," Weinberger told a National Press Club audience.

At the same time, special presidential envoy Richard B. Stone returned to the United States from a 12-day tour of Central America.

In Mexico City, he promised that the Reagan administration would not "impose our own agenda" on that region.

Weinberger, in response to questions, said one reason for continued U.S. aid to El Salvador is that it "is on the mainland of the United States, and we do have a responsibility for the defense of the continental United States, over and above all other priorities."

That defense, he continued, "conceivably can be made more difficult if further inroads are obtained on the mainland by forces that are demonstrably unfriendly to, and have aggressive intentions against, the United States."

Officials said the comment referred to possible increases in Nicaraguan and Cuban leverage among Central American nations.

Weinberger also denied that the United States is helping rebel forces try to overthrow the government of Nicaragua. "We are trying to interdict the flow of arms designed to overthrow the government of El Salvador," he said.

Stone, a former Florida senator, accused Salvadoran rebels of "seeking a propaganda advantage" by making public their offer last week to meet with him.

Returning to Andrews Air Force Base, Stone declined to say whether he would accept the offer, delivered to the American Embassy in Mexico City.

And he warned that further breaches of confidentiality "might well ruin" peace efforts.

The Salvadoran guerrilla group, the Farabundo Marti National Liberation Front, said in its offer to talk to Stone that it was still willing to hold unconditional talks with the Salvadoran government on ending the 3-year-old civil war. The government has agreed only to talks on conditions for participating in upcoming elections, an offer the front has rejected as insufficient.

The issue of structuring negotiations is expected to be high on the agenda when President Reagan meets with Salvadoran President Alvaro Magana in Washington on Friday.

On leaving Mexico City, Stone voiced the strongest administration support yet for a regional peace initiative by four Latin countries known as the Contadora group.

"I want to emphasize and stress that we support the efforts of the countries of the Contadora group to bring peace to Central America," he said. "We want to support their agenda rather than trying to impose our own agenda."

The Contadora group--made up of Mexico, Panama, Colombia and Venezuela, and named for the Costa Rican city where they first conferred--opposes any U.S. troop deployment in the area, has called for region-wide talks and the withdrawal of all foreign forces and has offered to mediate among warring guerrillas and governments in Nicaragua and El Salvador.

Stone said he had reiterated his support for those proposals at every stop on his 10-nation trip. "Although we have had good and fruitful discussions--we really have--still it is for them to find the agenda and the style and the procedures that they believe can most effectively get us to a peaceful and a justifiable solution," he said.

He declined to give details of his talks until he meets with Reagan. Besides Mexico, Stone visited El Salvador, Costa Rica, Guatemala, Nicaragua, Panama, Colombia, Venezuela, Honduras and Belize.