The National Academy of Sciences has voted to extend indefinitely its six-month ban on formal scientific exchanges with the Soviet Union in protest of the exile of dissident Soviet physicist Andrei D. Sakharov.

"We remain deeply concerned by [Sakharov's] continuing exile," the academy's ruling council said in a statement after the vote late Tuesday in Woods Hole, Mass. "Our suspension of those interacademy exchanges involving groups of scientists was a direct expression of this concern. This concern continues."

Last February the academy voted a six-month suspension of bilateral meetings, symposia and workshops with the Soviet Academy of Sciences after the Soviet Union arrested Sakharov at his Moscow apartment and exiled him to the city of Gorky, which is closed to Westerners.

In deciding to continue the suspension of group exchanges, the U.S. academy exempted individual exchanges by members and joint meetings on arms control and disarmament.

"Arms control and disarmament is a central problem for both our countries," the academy said in a resolution adopted by its council. "For this reason, the council will press for meeting at which scientists of the U.S.A. and U.S.S.R. can discuss thoroughly the technical aspects of this problem."