An international conference to review the workings of the 1965 Nuclear Nonproliferation Treaty heard warnings hee today that nations may begin to defect from the treaty unless more progress is shown by the superpowers in curbing the nuclear arms race.

Meanwhile, the conference heard a declaration from President Carter that the treaty "remains indispensable to the efforts of the nations to achieve a safer, saner and moe secure world" and a pledge that the United States "will give its fullest support to achievement of the treaty objectives."

The first warning of restiveness among the smaller nations about the workings of the nonproliferation pact came from Peruvian Ambassador Felipe Valdivieso, who said his country might renounce its participation out of dissatisfaction at the failure of the superpowers to live up to what the nonnuclear states regard as part of the bargain to curb and control nuclear weapons. Mexico is expected to follow Peru's lead and there is similar unrest among African, Arab and Asian signatories to the treaty.

However, an American delegate dismissed threats of defection as "wild talk" and said the United States was prepared "to listen to any practical demands" for improvements in the treaty workings during the next three weeks of the conference.

So far 114 nations have signed the nonproliferation treaty, and approximately half are taking part in this review conference. The pact is the most widely adhered-to arms control pact, but countries that have not signed include established nuclear powers China and France, as well as several nations that may have the potential for developing nuclear weapons or have done so on a small scale, such as Argentina, Brazil, Israel, Egypt, India, Pakistan, South Africa and Spain.

The treaty's terms prohibit nuclear powers from passing on nuclear weapons technology to others, while the nonnuclear nations pledge not to acquire atomic weapons of their own. Although a nonsigner, France has pledged to behave as if bound by the treaty.

Although Iraq has been being singled out primarily by Israel as the most likely potential new developer of nuclear weapons, Iraq in fact was one of the early signers of the non-proliferation treaty and an Iraqi diplomat has been unanimously elected chairman of this review conference.

United States Ambassador Ralph Earle, head of the arms control and disarmament agency, in the opening speech of the general debate, sought to offset in advance much criticism here of American nuclear policies by presenting a glowing summary of the American record in exports of enriched uranium to signers of the non-proliferation treaty, technical and financial assistance for nuclear programs, and cooperation with the International Atomic Energy Agency in its safeguards and control programs.

Nevertheless, there is much dissatisfaction among both the developing states and the industrialized states as well over American policies on such important aspects of the nuclear question as fast-breeder reactors, nuclear reprocessing and what are regarded as excessively complicated controls over uranium exports. For these reasons, countries increasingly have sought to find alternative sources of enriched or raw uranium.