The State Department said yesterday it will cut off $8.7 million in aid to Bolivia because the South American nation has not done enough to eradicate the coca crop used to manufacture cocaine.

Department spokeswoman Phyllis Oakley said the action was taken because Bolivia has not met crop eradication requirements ordered by Congress last year as a condition for American aid.

As a consequence, she said, Bolivia will lose $7.5 million of its scheduled $67.7 million of economic aid and $1.2 million of its $2.4 million in military assistance.

Luis Paz, minister-counselor in the Bolivian Embassy, said "we are doing our best" to eradicate the coca crop. The U.S. "sanctions . . . are very helpful to the traffickers, but not for my country or the United States," he said.

Bolivia has cooperated with the United States in attempting to curb illegal drug-trafficking and production. Under "Operation Blast Furnace" last fall, U.S. military helicopters ferried Bolivian police to the Beni jungle region to destroy cocaine laboratories.

But a State Department report issued earlier this month said coca eradication during the first half of the year was 25 hectares compared to 150 hectares during the same period last year.

State Department officials said the U.S. government had warned Bolivia that unless it eradicated 450 hectares by Sept. 30, the end of this fiscal year, it would lose aid.

Oakley told reporters Bolivia has "substantially improved its overall narcotics program," even though it is impossible for it to reach that target. She noted the two governments on Aug. 13 signed a comprehensive narcotics control agreement calling for eradication of 1,800 hectares of coca cultivation during a 12-month period. Eight major cocaine laboratories have been destroyed, Bolivia's antinarcotics bureaucracy has been streamlined and a crop eradication program has begun, she said.

Paz, however, complained about delays on the U.S. side in signing the accord and said "there is no coherent policy on this matter" in Washington.