The Washington Opera yesterday canceled the four performances of "Rigoletto" scheduled for Nov. 6, 10, 12 and 16 in the Kennedy Center musicians.

Gary Fifield, managing director of the company, said, "The continuing strike by musicians of Local 161-710 against the Kennedy Center has force us to take, most reluctantly, the action of canceling.

"Had we not taken this action, artists and production personnel from all over the United States and Europe would be arriving," he said.

"With scenery and costumes ready to be brought into the Opera House, and chorus rehearsals already underway, a complex and exceedingly expensive process would begin that under the circumstances would be totally irresponsible."

The opera company's situation is further complicated because of their plans to present "Rigoletto" and Mozart's "Abduction from the Seragio" in repertoire, with the Mozart due to open on Nov. 11. Fifield said that "If a settlement is reached before Wednesday, Oct. 25, we still have time to go forward with rehearsals for "The Abduction."

The terms under which the Washington Opera uses the Kennedy Center Opera House orchestra for its productions made it impossible to secure other musicians to play its performances.

In the meantime, the National Symphony Orchestra strike, now ending its fourth week with no sign of settlement, yesterday brought the cancellation of next week's concerts in which Mstislau Rostropovich was to have conducted, with violinist Isaac Stern as soloist on Tuesday, Wednesday and Thursday nights.

In addition, the continuation of both strikes brought postponements of two other orchestral concerts. The Pittsburgh Symphony, scheduled for the Kennedy Center on Sunday, has been postponed to April 1, and the Philadelphia Orchestra program, scheduled for Monday, has been postponed to April 9.