Substantial numbers of American drivers, guards and other support personnel will replace local employes in U.S. embassies and consulates in the Soviet Union and other East European countries under a plan announced by the State Department yesterday.

Spokesman Charles Redman said the program, designed "to counter intelligence threats against our embassies abroad," had been set in motion before President Reagan's Nov. 1 executive order tightening U.S. security through the use of lie detectors and other means.

Secretary of State George P. Shultz has asked for $5.9 million in fiscal 1986 and $17.9 million in fiscal 1987 to replace one-third to one-half of the Soviet nationals employed in the U.S. Embassy in Moscow and the U.S. Consulate in Leningrad with American workers, officials said.

Initially this would involve hiring 22 U.S. citizens under contract to be "maintenance workers" in the Soviet Union, and 50 to 60 Americans under contract for staff support positions.

About 200 Soviet citizens are currently employed in U.S. diplomatic missions in the Soviet Union. "We will retain Soviet local employes only in those positions which could not be efficiently [filled] by Americans," a State Department official said.

A parallel program of replacing local workers with Americans in the six Warsaw Pact countries of Eastern Europe is expected to cost about $2.3 million in fiscal 1986 and $6 million in fiscal 1987. The countries involved are East Germany, Poland, Czechoslovakia, Hungary, Romania and Bulgaria.

The replacement program, undertaken by Shultz at strong congressional urging, is reported to be under scrutiny by the Office of Management and Budget.