Want to start a new international banana business, with plantations, banana boats and all? John Pierce Clark is the man to see.

"That's the kind of project we're setting up to do," says Clark. "It's a little wild, but a good example, because the regulatory agencies would be so important."

Clark is President of Pierce International, a new Washington firm organized to be merchant bankers doing business primarily in the Third World. It was formed by Clark and four associates as a spinoff from Porter International, a similar firm that continues in business.

The new venture was formed, Clark explained, because of the growing importance of Washington as an international financial market.

"Its no longer such an uphill struggle to do this kind of business in Washington," he added. "Banking here has developed to the point that the market is much more easily approachable."

Pierce Internationsl's primary business will be syndicating medium term loans from the Third World, mostly Latin America. The company will put together packages, placing the loans in the Eurodollar market, with regional American banks and Japanese and Europeon financial institutions.

Clark said his group has placed two Venezuelan housing project financings, of 360-day $100 million dollar notes, and has two similiar deals underway.

The firm also handles trade financing for American companies doing business in Latin America, Africa and the Far East and does consulting for companies entering the Third World markets.

Such activities have been the turf of big New York banks, Clark added, but are now opening up to others as international banking spreads across the country.

Officers of the new firm, in addition to Clark, who previously worked at the Inter-American Development Bank, are:

Jack Hood Vaughn, former director of the Peace Corps and assistant secretary of state for Inter-american affairs, who now represents David Lillienthal's Development and Resources Corp. In Iran.

David Gregg III, a former executive vice president of Overseas Private Investment Corp. here and an executive of Blyth Eastman Dillion & Co.

T. Graydon Upton, former assistant secretary of the Treasury and executive vice president of the Inter-American Development Bank.

Martin Reingold, a Venezuelanbased financial consultant who is the company's representative in that country.