Thomas C. Schelling, professor of Economics, has been asked by the State Department to develop a "systems analysis" approach to foreign policy.

He is requesting a leave of absence for the 1967-68 academic year so that he can serve as a full-time consultant to the Department while making his study.

What the Department wants to know is how "systems analysis" and "program budgeting" -- techniques with which Robert McNamara overhauled the Defense Department in the early '60's -- can make more effective the $5 billion Federal agencies spend annually in assistance to foreign countries.

The White House and the Bureau of the Budget have been trying to extend these techniques to other departments for more than a year. One result is the upcoming reorganization of the Health, Education and Welfare Department. Another is Schelling's study.

May Revamp Budget

There is no indication, however, that the study will lead to any major reorganization within the State Department. Though Schelling's duties are still being defined, it is clear that the Department is most interested in revamping its budgetary process.

Schelling will be asked to find better ways of relating the money spent in various programs to foreign policy objectives. The Department, for example, has no easy way of finding out what proportion of all the money that goes to a given country is helping to raise its standard of living, as opposed to aiding its army or changing its trade policies.

To find a method Schelling will have to examine how money is spent not only by the State Department but also by related agencies -- and, to some extent, by the Defense Department.

He will also have to look into the way that information about expenditures is chanelled back from foreign countries through the State Department to its top administrators.

It will be the second time that Schelling has helped to shape programs of assistance to foreign countries. In 1950 he worked under Averell Harriman, helping to develop the foreign aid program -- the annual package of military, technical and economic assistance that has become so familiar since.

Schelling, who came to Harvard in 1959, was acting director of the Center for International Affairs last year.