She's out to sell private enterprise in the third world

''There's a great deal more receptivity now in the developing world to the whole concept of the private sector.''

That's what Elise Ravenel Wood du Pont finds, and it should make her new job easier. Mrs. du Pont is head of the Agency for International Development's Bureau for Private Enterprise, which was founded last year. The bureau is charged with bringing the benefits of free enterprise to the third world - a reflection of the Reagan administration's belief in the powers of capitalism.

Mrs. du Pont - a lawyer specializing in corporate issues - is married to Pierre S. du Pont IV, governor of Delaware. But for a while she will be spending less time in the family's traditional state and more time in places like Thailand, Kenya, and the Ivory Coast.

''What we're doing here is looking at ways to promote the indigenous private sector in the developing world, and how to facilitate the American private sector's access to the developing world,'' said Mrs. du Pont during a recent interview in her State Department office.

By pointing US companies toward profitable development projects, her bureau hopes to lure private money into the third world with relatively little government investment, thus gaining more development bang per foreign aid buck.

''I think our rationale is very much the administration's rationale,'' Mrs. du Pont says. ''We're looking for the most cost-beneficial ratio for the taxpayer, and we are looking for ways that the private sector can move in and take up some of the slack in the financial end of foreign policy.''

For instance, the bureau might produce a study on the feasibility of building a vegetable processing plant in a certain country. It could line up a local entrepreneur, arrange financing to augment his funds, and present a package of American machinery, marketing, and management training services. Both the local private sector and US exports would be bolstered.

The bureau might also put in a little money of its own. Its budget includes ''a centrally funded pot of money, $30 to $35 million'' earmarked for especially attractive investment opportunities, says Mrs. du Pont. The bureau, though, will never be more than a minority shareholder.

The Bureau for Private Enterprise has also been given command of several longer-running development efforts. AID's Housing Investment Guarantee program, which guarantees repayment on private-sector loans for third world shelter, has been moved under the bureau's aegis. So has the International Executive Service Corps -- a group of retired executives that put their expertise at AID's service.

Initially, the bureau will seek an outlet for its services through trade reconnaissance missions. Ten countries have been selected: Indonesia, Sri Lanka, Thailand, Pakistan, Ivory Coast, Kenya, Zimbabwe, Jamaica, Costa Rica, and Egypt. These nations were chosen as being both strategically important to the United States and possessed of a nascent private sector, growing and interested in Western aid.

The first mission -- to Indonesia last October -- included several businessmen, an Indonesian-speaking lawyer, and an agribusiness specialist. It identified some good opportunities for agribusiness and saw a need for advice in forming a national stock market, says Edgar Harrell, a bureau official who headed the trip.

''We generally come into the country because the country wants us there,'' says Mrs. du Pont. ''We look at the capital markets, need for management training, investment opportunities, natural resources -- what the indigenous private sector has to offer.''

On the other end of its effort, the bureau hopes to promote interest among US businessmen by publishing lists of needed technology and expertise, as well as developing contacts through groups such as the US Chamber of Commerce and the Business Roundtable.

It would probably prove difficult to bring capitalism to a country committed to a centralized economy, or lacking a tradition of entrepreneurial enterprise. Will the activities be limited to the better-off less-developed nations, such as those picked for reconnaissance missions?

''We're not trying to change the world,'' says Mr. Harrell, one of Mrs. du Pont's two deputies. ''We're trying to work with those countries, like Jamaica, that definitely want to support private-sector development.

But can the US private sector be persuaded to enter a country that might not be an attractive investment, like Bangladesh?

''We'll cross that bridge when we get to Bangladesh,'' Mrs. du Pont says. ''This is an evolving program.''