Warning that the international community is unprepared to deal with a new world food shortage, the director general of the United Nations Food and Agriculture Organization today urged the adoption of a five-point plan to improve the precarious situation.

At a meeting here of the permanent representatives of FAO's 90 member states, Director General Edouard Saouma said the recent breakdown of negotiations for a new international wheat agreement "represents a major setback to our hopes of achieving better food security."

A major goal of the U.N. conference in Geneva, which after years of talks adjourned inconclusively Feb. 14, was to establish some form of coordinated system of national food reserves that would achieve price stability and help prepare the world for serious food stortages such as those in 1972 and 1974.

The breakdown of the negotiations also jeopardizes the proposed revision of the 1971 food aid convention. Before the talks collapsed, donor nations had agreed to almost double the annual minimum target of 4.6 million tons of grain laid aside for emergencies.

Given the pressing need to secure food supplies against possible shortages, Saouma said, FAO has come up with a plan for a system of nationally held and internationally coordinated food stocks that would be released according to agreed guidelines in times of shortage.

Without such a plan, he warned, a replay of the world food crisis of the early 1970s is likely. As then, world grain stocks are high. But since there are no legally binding provisions for coordination and since geographic distribution of the stocks is uneven, they could quickly be drained in the event of serious crop failures.

According to FAO officials, a reserve supply of 75 million tons of wheat is required if another major food shortage is to be avoided. Under the plan, almost half would be held in developing countries.

Current surpluses of wheat, which have not necessarily been earmarked as reserves, amount to 80 million tons. But these are concentrated in only a few areas like North America. The United States, for example, holds 30 million tons of surplus wheat and 40 million of the 75 million tons of surplus coarse grains such as corn.

Grain stocks in the developing countries have diminished. Between 1977 and 1978 alone, the less developed countries' imports of grains jumped to 70 million tons from 55 million.

The FAO plan which will be discussed in April by a committee on world food security, calls for the unilateral adoption by all nations of reserve stock policies and targets, selection of criteria to guide national decisions on the release of such reserves and the adoption of measures to assist developing countries to meet their food import requirements.

The five-point plan also calls for aid to strengthen developing countries' own food security programs and support for regional and multilateral programs to cope with food deficits.

To date, 39 developing countries have food stock policies but only 11 have met their targets. Even fewer grain-exporting countries have such policies and only the United States has achieved its target for emergency stocks.