The summit nations' finance ministers, in three sessions of their own last weekend during the heads-of-government meeting at Williamsburg, Va., were unable to agree on a formula that would bring them into regular contact with trade ministers.

Despite strong American interest in resolving the question, the finance ministers put it off until they meet again just prior to the joint annual session of the World Bank and International Monetary Fund in September. This may rule out Treasury Secretary Donald T. Regan's hope that a second trade/finance ministers meeting could be held in September.

Regan, along with U.S. Trade Ambassador William Brock, had organized an initial finance/trade ministers dinner-meeting in Paris three weeks ago, as a follow-up to the ministerial session of the Organization for Economic Co-operation and Development.

U.S. officials said yesterday that there is growing acceptance of the proposition that trade and finance problems are linked, and that the ministers responsible for each area should somehow be brought into closer contact.

But it was clear at Williamsburg that there is opposition to setting up a new, formal structure where finance ministers would meet trade ministers on an equal footing. In addition, Gaston Thorn, president of the Common Market organization, voiced opposition to trade/finance ministers meetings limited to the seven summit countries: the nonsummit European nations don't want to be excluded, and the European summit nations are sympathetic to this view.

West German officials suggested at the Williamsburg finance ministers' meetings that informal trade/finance ministers' dinner-sessions be held prior to the annual Spring OECD ministerial meeting in Paris. That would bring all 24 in the OECD industrial group into contact with their finance ministers.

The Regan-Brock initiative was based on a belief that finance ministers and trade ministers rarely consider each others' increasingly interrelated problems. Trade ministers have become especially frustrated by the wide swings in foreign exchange rates, which they feel have inhibited the free flow of trade.

Regan and Brock also fear that Third World nations, struggling to refinance their $600 billion debt, will fall further behind unless they are able to boost their export earnings.

Nontheless, opposition to the Regan-Brock plan was evident from the beginning. The French refused to participate in the Paris dinner-meeting, arguing that it interfered with the normal summit preparation process. The Japanese do not like to have their finance and trade ministers in any joint meeting where their foreign minister, who establishes the government "line," is not present to referee differences. Therefore, the Ministry of Finance sent only a lower-level figure.

Lower-ranking finance officials were also sent to the Paris session by Germany and Great Britain. But those who did participate found it surprisingly useful, both German and American sources say.