President Carter, in his first speech since his reelection defeat two weeks ago, said yesterday that the cause of human rights, which he made the centerpiece of his foreign policy, will endure long after he leaves the White House.

Addressing the opening session of the General Assembly of the Organization of American States, the president said that in the last four years "a new conscience has been awakened" and is advancing "a concept of human rights that is not unique to any country, nor even just to this hemisphere, but is universal."

"Some claim," he continued, "that Jimmy Carter elevated human rights and democracy on the inter-American agenda and that the agenda will change when I leave office. They are wrong. Hemispheric support for human rights is an historic movement."

Carter made no mention during the speech of President-elect Ronald Reagan. But the thrust of his message was an indirect warning to Reagan -- who has been highly critical of the administration's human rights policy -- not to reverse the human rights initiatives that the administration set in motion. In the process, the president strongly defended his support for the Panama Canal treaties, which, while not a major issue in the 1980 presidential campaign, have been the target of some of Reagan's most biting criticism in the past.

"After four years of practical experience, I'm more convinced than ever that the future we desire lies in recognizing yearnings that are common to individuals and to nations alike," Carter said. "As individuals the people of the Americas yearn for basic human rights. They desire personal liberty to be free from torture and arbitrary arrest, to participate in making the basic decisions that shape their own future, to have adequate food, health care and education."

"Some would ignore or resist these treasured rights, the rights of individuals and the rights of nations," the president continued. "But the future lies with those who cherish them, and who are willing to defend them."

"Today no government in this hemisphere can expect silent assent from its neighbors if it tramples the rights of its own citizens," he said. "The costs of repression have increased, but so have the benefits of respecting human rights. I pray that this progress will continue, although I know from experience that progress is not always easy as we defend human rights."

While he devoted the bulk of his speech to a general discussion of human rights policy, Carter also called on the OAS to insist on "a strict policy of non-intervention" in the internal disputes in Nicaragua and El Salvador. He also said it is "imperative" that those nations that have not signed a treaty banning the spread of nuclear weapons in the Western Hemisphere do so "to set an example for other nations in other regions of the world."