The Carter administration has decided to supply $5 million in food aid to the People's Democratic Republic of Laos for humanitarian purposes, Congress and the Laotian government were informed yesterday.

State Department officials said the aid to the communist-led regime was justified on the grounds of "basic human need" in view of the servere malnutrition and potential widespread starvation resulting from a poor rice harvest this year.

Laos had appealed to all nations last August for aid to head off a "disaster" caused by an impending food shortage, and in January the Laotian government made a "very polite, correct and reasoned appeal" to the U.S. embassy in Vietiane for bilateral assistance, according to the State Department officials. Laos is the only Indochinese nation with which the United States has diplomatic relations.

The Carter administration, which has spoken often of meeting humanitarian needs, recently has been criticized in the press for failing to act on the Laotian request.

Officials said the administration's failure to approve food aid until now was based in part on a reluctance to undertake a possibly controversial foreign policy action at a time when the Panama Canal treaties, the Middle East arms package and other controversial foreign affairs issues were before Congress.

State Department officials said the aid to Laos is unrelated to the fast-growing tensions and public controvery in Indochina, where Vietnam and Cambodia are engaged in intermittent border fighting, and Vietnam and CHina are involved in a war of words.

Some 30,000 to 40,000 Vietnamese troops and civilian technicians are reported in Laos, which is considered under strong Vietnamese influence. Hundreds of Soviet advisers also are reported on hand.

The Soviet Union and other Soviet-bloc states, as well as Western European and some Third World countries, have pledged to provide more than 80,000 tons of rice to Laos, but an additional 30,000 tons are needed to meet the country's needs, according to U.S. officials. The U.S. pledge will provide about 10,000 tons of rice under Public Law 480, the "Food for Peace" program.

The United States has informed Laos it will consider additional food aid later if it is clearly needed and if the state of U.S. Laotian relations is satisfactory Relations between the two countries were described by officials here as "cool but correct."