Representatives of two Fairfax County teacher organizations voted yesterday to ask their memberships to reject a school system administrative committee's offer for a 3 percent salary increase next year--half of what teachers requested.

Marilyn Rogers, president of Fairfax Education Association, which represents about 6,300 of the county's 7,400 teachers, said this is the first time in a decade that teachers and school officials have been unable to reach a compromise on salary issues. The FEA is seeking a 6 percent pay raise for employes while the smaller Fairfax Federation of Teachers is asking for a 7.5 percent increase.

"We feel like 3 percent is a real insult to teachers," said Mike Mitchell, president of the FFT.

But Rogers said Fairfax teachers, whose salaries range from $14,910 to $33,928, aren't blaming the impasse entirely on the school administration. "The county supervisors are the bad guys," said Rogers. "It was their interference so early in the process that caused the problem."

This summer the Board of Supervisors asked all county agencies to limit budget request increases for next year to a maximum of 5.85 percent. The school board endorsed that proposal in September.

"After we looked at all our mandated costs and other expenses," said R. Warren Eisenhower, who represented the school system in discussions with teachers, "we only had enough left to fund a 3 percent increase in salaries." Under Virginia law, public employes cannot conduct formal negotiations with government agencies, but can participate in informal talks with the administration.

Eisenhower said the proposed 3 percent increase for the school system's 12,000 employes will cost $10.7 million. The administration team that has been meeting with the county's two teacher organizations since late August, will recommend the 3 percent increase to school Superintendent William J. (Jack) Burkholder. Burkholder, in turn, will decide what figure to include in the budget he presents to the school board in January.

Rogers said teachers will lobby the school board for an increase in the salary offer, but will concentrate its efforts on supervisors. "There's all kinds of ways we can make their life uncomfortable . . . with elections coming up next year," said Rogers.