The United States and other friendly countries are seeking urgent international aid to prevent Haiti's recent political triumph from sinking in the economic morass left behind by the ouster of president Jean-Claude Duvalier.

Representatives of the major donor governments have scheduled a first meeting Friday under auspices of the International Monetary Fund in Washington to seek emergency loans for the largely depleted Haitian Treasury, diplomatic sources here reported. The most immediate need is for cash to buy petroleum, they said, since present stocks were insufficient to finish the month without danger of shortages.

Lines at gasoline stations and electricity brownouts were critical in fomenting the first street disturbances in Gonaives and Cap-Haitien last November, which quickly developed into a nationwide uprising. This led to the downfall Feb. 7 of Duvalier after 29 years of rule by him or his father.

With the political climate here still unsettled under a military-dominated provisional government, Haitian officials and foreign diplomats are eager to avoid similar hardships that could stimulate more unrest.

Many of the youths who participated in demonstrations against Duvalier came from among the 50 percent of the population that is unemployed and often poor to the point of hopelessness. They still are hanging around the streets, one former government official pointed out, with a new awareness of their power to affect events.

Against this background, France and the United States, the two countries with closest ties to Haiti, have announced dispatch of urgent food shipments since Duvalier's fall. Canada, which also has been a major donor, sent foreign aid officials this week for talks with Lt. Gen. Henri Namphy and his National Council of Government on a similar Canadian offer.

The United States has scheduled about $50 million in financial and food aid for this fiscal year, slightly down from 1985. Some additional funds may be sought from Congress now that the dictatorship here has ended, a knowledgeable source predicted.

Secretary of State George P. Shultz announced last week that previous withholdings of aid because of human rights violations have been lifted since Feb. 7. Roughly half of U.S. aid is in food, distributed largely through private agencies to avoid handling by Haitian ministries, which are described by international aid officials as inefficient and often corrupt.

France and Canada each provide under $30 million in aid per year, and West Germany about $20 million. Any changes in their plans have not been announced. But a mixed Franco-Haitian aid commission has set a regularly scheduled review for this summer, a French diplomat said.

A foreign economist estimated that Haiti's biggest need, after the quick injection of cash for oil imports, is a new standby agreement this spring from the International Monetary Fund. The government has accumulated more than $2 million in arrears on previous IMF loans and also has fallen behind on repayments to Canada and Argentina, the economist said.

A new loan would allow rollover of these debts and give the IMF endorsement that is crucial for additional loans from other governments and organizations, he added. "One cannot overestimate the value of a standby for Haiti," the economist declared.

Many Haitians have expressed belief that government coffers are empty because Duvalier and his family escaped with millions of dollars from the Treasury in their suitcases. Responding to these complaints, the ruling council announced yesterday it will seek to recover Duvalier's fortune through contacts with the World Court, the Organization of American States and the Organization of African States, "as well as certain Third World countries."

In a similar vein, the newspaper Le Matin reported that Duvalier had a yacht in Miami worth $450,000, two boats at his beach house here worth $160,000 and a second yacht under construction in West Germany worth $3 million.

Foreign economists said, however, that there is little indication Duvalier pillaged the Treasury any more in his final escape than he had over the years since succeeding his father in 1971. For that reason, several diplomats said, it is unlikely that the new government's contacts will be anything more than a gesture.

Instead, now is the time to dismantle the economic structures that permitted Duvalier and his associates to carry out corrupt practices, these diplomats said.

One economist said, for example, that the state-owned oil company should be abolished. Most of its contracts have prices above current Caribbean spot rates, raising suspicion that they were negotiated to leave room for official corruption, another diplomatic official said.

In addition, such basic necessities as rice, cooking oil, beans and cement cost more here than in neighboring countries, partly because they have been distributed through monopolies granted by the Duvalier family to sympathetic businessmen, the economists said.