The State Department and the Foreign Service are often maligned. Fudge factory and cookie pushers are common epithets. The State Department has problems, and I have sometimes been among its critics. Yet the department is vital to the nation, and Foreign Service officers are among the most dedicated, capable and unappreciated of public servants.

The prospective unprecedented cuts in the State Department's budget and personnel jeopardize the national interest. Its modest progress in strengthening its international, economic, political-military and foreign language expertise will be reversed. For example, the department offers an invaluable perspective in foreign economic policy, but the already-too-few economic specialists will be especially hard hit by the cuts. Moreover, a 1986 departmental study highlighted disturbing deficiencies in officers' foreign language competence in Arabic, Chinese, Japanese and Russian, yet the proposed budget reductions will eliminate incentives for meeting this critical need. There are many other potentially negative results, including loss of talented Foreign Service Officers.

Flailing the State Department has long been a popular pastime among many legislators, some of the public (who distrust ''striped pants'' diplomats) and not a few academics. The department lacks a public constituency and the political clout of most other Cabinet departments. But while some of the forthcoming reorganization of bureaus may be salutary, and the elimination of the Latin American bureau's public diplomacy office is certainly welcome, it is time for Congress to consider what is at stake. America's ability to pursue its national interests is about to be weakened in identifiable ways. DUNCAN L. CLARKE Washington The writer is a professor at The American University's School of International Service.