The will to work together

President Mitterrand's call for a ''world plan'' to reconstruct the international economic system helps put the spotlight on the forthcoming summit meeting at Williamsburg, Va. Economic summits tend to draw a public yawn, even though the issues they address are of paramount importance. So the French leader's proposals should at least stir public debate and interest.

Today the Western industrial nations are treading uncharted paths. They confront enormous change: namely, a restructuring of the global economy as a result of the declining economic weight of the United States (down from a high 70 percent to 40 percent of the gross world output) and the meteoric rise not only of Japan and the European Community but of a whole number of newly industrialized countries (NICs) - South Korea, Taiwan, Brazil, and others. At the same time they must deal with the growing financial burdens of the poorer countries if the international financial system is to remain stable. And all this in a climate of lingering recession, high unemployment, and demands on public treasuries.

Is international economic planning the way to meet the challenge? Or a reorganization of the world monetary system? Most Western nations will be cool to the French idea. Indeed what is needed are not new organizations or systems - but the political will and resolve of each member of the global community to make existing institutions and arrangements work. There are mechanisms galore for coordinating policies (all established in the post-World War II period). There is not always, however, a sense of mutual responsibility, a willingness to pursue wise national policies and to eschew the excessive nationalism standing in the way of cooperation.

As the major industrial nations prepare for the Williamsburg gathering, the prescriptions for progress are quite clear:

* The rich countries must manage steady economic growth in a noninflationary atmosphere. This requires gradual but constant progress in reducing budget deficits so that the financial markets can take care of private borrowing needs without creating fears of future inflation. The US especially, whose economy remains dominant, must not weaken in its efforts to bring the federal deficits - and interest rates - down. Unfortunately, Congress seems to be flagging.

* The industrial OECD countries must agree not to compete unfairly with each other. Japan, for example, must be sensitive to not flooding foreign markets with its goods, while Europe must take care not to shut out Japanese exports which are a legitimate part of Japan's entry into sophisticated manufactures. It will take compromise, restraint, and understanding to stem a new wave of protectionism.

* There must be proper financing of third-world debt needs through private banks and such international institutions as the World Bank and the International Monetary Fund. It is less important that total third-world debt - now in excess of $600 billion - be paid off than that foreign countries and companies be strong enough to service their debt. Expanding third-world nations can be expected to have actually increased credit needs for many years to come, but - again - their export earnings must be sufficient to ''cover'' their debt-service needs. Fair trade and further relaxation of rules in GATT (the General Agreement on Tariffs and Trade) are just as crucial to their long-term financial stability as are their domestic economic policies.

* Many poorer nations will continue to need development aid through the World Bank, the IMF, and other institutions. There is disinclination in time of recession to keep up foreign aid budgets. But the industrial nations must not lose sight of the fact that jobs are created and exports fostered as the result of such assistance. Whatever the past waste, aid doesm work - witness India, South Korea, and many other recipients now on the road of sturdy growth.

* East-West trade should be expanded as well. The Reagan administration seems to want to put a brake on what it regards as ''help'' for communist economies. Certainly the Western nations must tighten the rules governing export of sensitive industrial equipment. But it is a question whether trying to isolate the Soviet-bloc countries and slow their economic growth is wise policy. In fact US trade sanctions - on grain and oil technology - have dramatically hurt the US , according to a congressional report issued this week. Instead of waging economic war with the East, efforts should be made to draw the communist countries into the world economic system - thereby giving them a stake in stability and peace, forcing them to reform in order to compete, and expanding the total economic pie for everyone.

As for President Mitterrand, one can appreciate France's difficulties brought on by poor early economic policies and the desire to gain some relief from the strong US dollar which is pushing up the cost of oil and other imports. Perhaps some relief is in order. But whether a complete revamping of the monetary system is called for in today's uncertain climate is doubtful. The more prudent course for the Western nations is to stick with present institutions, keep recovery on track, and ride out any uncomfortable dislocations. No period of massive change is easy. But it need not be painful - if there is the will to work together.