French Foreign Minister Jean Francois-Poncet intends to make a public condemnation of Communist intervention in El Salvador during a visit to Washington next week French officials said today.

The evidence of an outside Communist role in the troubled Central American nation given by special U.S. envoy Lawrence Eagleburger to the French government in Paris yesterday and to the Atlantic Alliance in Brussels were entirely convincing, authoritative sources here said today. Eagleburger is expected to be named assistant secretary of state for European affairs.

U.S. sources said that material presented by Eagleburger included evidence that a large proportion of the arms reaching Salvadoran leftists is U.S. weaponry captured in Vietnam. Those sources said that the arms, which also include material manufactured in Eastern Europe, are first shipped to Cuba and then infiltrated into El Salvador via Nicaragua, according to electronic and other intelligence data presented to European officials.

The American sources said the information soon would be made public in the United States.

Gaston Thorn, head of the Executive Commission of the 10-member European Economic Community told Eagleburger today that the Europeans would hold up their food and medical aid to El Salvador pending an investigation with the Red Cross, which was to distribute the aid, to make sure that it would not benefit the Salvadoran government's guerrilla adversaries.

On Monday, the Community had decided on a $1.5 million aid package for El Salvador. But on Tuesday, Eagleburger handed Thorn a letter from Secretary of State Alexander Haig asking that the aid be held up.

The European aid program was originally intended for distribution to the Salvadoran population without political discrimination in obvious response to widespread public sympathy for the guerrilla cause, especially in the left wings of West European Socialist parties, including those in power such as the West German Social Democrats.

The Socialist International, headed by former Wester German chancellor Willy Brandt has given financial and moral support to the guerrillas in response to pleas by Salvadoran opposition leader Guillermo Ungo, a vice president of the International.

Eagleburger's next stops on his European tour are the Netherlands and Britain in a campaign that the West European press is depicting as a test case of Western backing for the new U.S. administration.

Some French sources said that France would be inclined to advise the Reagan administration that the aid to the Salvadoran government should also include encouragement of basic social reforms.