French President Valery Giscard D'Estaing called yesterday for a new European security conference that would seek to negotiate a balanced reduction in the "enormous arsenals of conventional weapons" of the Warsaw Pact and NATO countries.

The French president, addressing the U.N. General Assembly's special session on disarmament stressed the need to find a way to reduce the Warsaw Pact's superiority over NATO in conventional weapons.

Vice President Mondale, appearing before the disarmament assembly Wednesday, noted that Warsaw Pact forces have three times as many tanks as NATO.

"The threat overshadowing Europe does not come from the accumulation and sophistication of nuclear weapons alone," Giscard declared. "It also stems from the presence on our continent of enormous arsenals of conventional weapons, and the disparity between them."

Giscard said France would transmit invitations through diplomatic channels today to all the countries that took part in the 1975 European security conference in Helsinki seeking their participation in the new European disarmament talks. He said the new talks probably could not be held before next year.

Invitations to the talks would go to the United States, Canada and the Soviet Union, he said, as well as to all East and West European nations.

While the French president endorsed the efforts of the two super-powers to negotiate reductions in their stragegic arsenals through the SALT talks, he warned that "nuclear disarmament would soon reach its limits" if steps were not taken to reduce the imbalance of conventional forces in Europe.

"The visible inequality in conventional weapons constitutes a block to nuclear arms reductions," he told the 145-nation conference.

In the course of his address, Giscard formally unveiled a number of ambitious arms control proposals. He suggested creation of a new international agency that would monitor arms agreements through use of satellites, and called for establishment of a world institute for disarmament studies partterned on the International Monetary Fund.

At a press conference following his speech, however, the French president turned defensive at the suggestion that his country take the lead in arms control by halting further testing of nuclear weapons, and curtailing its high-powered efforts to sell tanks and warplanes to Third World countries.

"France is in favor in principle," he declared. Nevertheless, he argued that the superpowers had staged far more nuclear tests and were selling more weapons to the developing nations than France.

Giscard argued that it would "not be feasible" for France to unilaterally curtail arms sales "as long as there is no common agreement between the United States, Soviet Union, United Kingdom, France and West Germany.

The French president also balked at responding to questions about the Soviet and Cuban role in Africa, contending that this was "not relevant to disarmament."

Giscard, who dispatched troops to Zaire last week to aid that government in repelling rebels who had invaded Shaba Province, also said he favored Africans themselves being responsible for security in Africa."

The French president said creation of a European force to help maintain peace in places like Shaba should not be necessary.

"We should have an African corps made up of Africans," he said.