District of Columbia public school teachers may strike when schools open Sept. 8 unless they have a contract with the District Board of Education, Washington Teachers' Union President William H. Simons said yesterday.

"I'm quite sure that teachers, after 11 years, will not return to servitude and work without a contract," Simons said at a news conference.

Simons asserted, and District school officials agreed, that negotiations for a new contract have been bogged down for more than three months over a procedural issue and that substantive bargaining has not begun. The contract between the teachers and the board expired July 25 after being extended from its original expiration date of Jan. 26 at the request of the board and the acquiescence of the union.

Conrad Smith, president of the board, said the delay was the union's fault. "We're ready right now to sit down and negotiate a contract," Smith said, "and if there is no contract, it's because the union has refused to sit down and negotiate."

Both sides agree that the issue holding up negotiations is the question of how many hours teachers serving on the union negotiating committee can be away from their classrooms without losing pay. The current contract sets no limitations. The board has proposed limiting the amount of excused leave for members and alternates of the union's negotiating team employed by the board. That limit would be six members at 80 hours, for a total of 480 hours. Simons said the union negotiating team generally has about eight teachers on it.

The board has suggested submitting the question to a neutral third-party for "fact finding," which involves a report expressing an opinion as to what should be done. Simons said the union has recommended submitting the question to binding arbitration.

Union and board negotiators met once in March to discuss the board's "prenegotiated agreement," setting out the ground rules for contract negotiations. Unable to reach agreement on the ground rules, the two sides did not meet again until July 17, when they met with a mediator to discuss the issue.

Simons said yesterday that the union reluctantly agreed to extend the contract when the board requested an extension last January. But the board, he said, gave the union the "cold shoulder" when it asked the board in mid-July to further extend the present contract through Oct. 31 to give both sides more time to bargain.

When the union asked the board to further extend the contract, Simons said, the board responded by taking steps to stop the deduction of dues from union members' paychecks. About 5,000 of the District's 6,500 elementary and secondary school teachers are union members, according to a union official. Simons accused the board of "union-busting" tactics.

Simons said that the question of how much time teachers could have outside the classrooms to negotiate ceased to be an issue once school ended June 16. At that time, Simons said, teachers were available to negotiate but the board refused.

In response to a question, Simons said that the union had not yet asked the teachers for a strike vote. But he said that course was not option open to the union. Simons declined to say what other options there might be.

The last time the union called a strike was in 1972 and it lasted about 2 1/2 weeks. The board stopped collecting union dues once before, in 1975, during a work slowdown by union teachers protesting the board's cancellation of an extended contract. The board and the union negotiate only working conditions, since teachers' salaries are set by the D.C. City Council through legislation. The City Council has indicated that teachers, firemen and police officers will get the same percentage increase that federal officials receive.

Smith said that the dues deduction, or checkoff, was stopped on July 25 because the contract expired and not as a response to the union's request for an extension. It's not a question of extending the contract now," Smith said. "It's a question of getting a new contract, because we do not have a contract now."

Kenneth W. Nickoles, director of labor relations for the board, said yesterday that the contract that just expired had taken 2 1/2 years to negotiate. Therefore, he said, the board was not willing to begin negotiating when school ended in June until the ground rules were set because the board thought it doubtful that there would be time to complete a new contract before the full opening of school. If a contract were not set, Nickoles said, the board would have to "pull the stopper out of the negotiations" once they were under way.

"It's a matter of putting the horse before the cart," Nickoles said. He said the board was concerned about "disruption of the educational process" caused by the frequent absence of negotiating teachers from their classrooms when the negotiations are protracted.

Nickoles deneid that the board was trying to break the union. "If we were going to try to bust the union," he said, "there are a number of things we could go about to do that . . . We are trying to negotiate a contract." Nickoles said that the board considers itself "in negotiations with the teachers."