Physicians responsible for the care of more than 100,000 Washington-area residents may go on strike Saturday unless they receive an acceptable contract offer, the president of the Group Health Association physicians' union said yesterday.

The union, whose president previously has said that a strike was not contemplated, has file a formal notice with the Federal Mediation Service and with the 109,000-member Group Health Association removing legal barriers to a strike after 8 a.m. saturday. Dr. Norman Lieberman, president of the union said yesterday that a strike was now "a possibility."

GHA, the Washington area's largest prepaid group health plan, has been negotiating a contract with the 55-member union since January. Lieberman indicated that the proposed salary package was acceptable. The proposal calls for average pay for all physicians to go from the present $53,000 to $60,000 and then to $66,000 in 1978 and the highest paid specialty - obstetrics/gynecology - to go from $71,500 now to [WORD ILLEGIBLE]in 1979.

Both Lieberman ans GHA president Harold Wool agreed in separate interviews yesterday that three major issues remain to be settled: malpractice insurance, outside employment by physicians and hours of work.

GHA is scheduled to deliver a formal, final offer to the union today so that the union membership can vote on the proposal at a meeting called for this evening. Lieberman said the final contract offer outline at the last negotiating session was unacceptable to the union's negotiating team.

"If nothing changes between now and then," Lieberman said yesterday, "I'm sure there'll be some kind of a strike vote. I really don't know if it'll pass. It depends how angry they are."

Dr. Donald Mitchell, a dermatologist and a member of the negotiating team, said that if the contract proposal is not changed by GHA. "You'll see physicians on the street Saturday morning . . .They've had all they can take." Mitchell had told a reporter several weeks ago that he could never support a strike. Yesterday he said he would "walk the picket line" if a strike were called. "I'm the most surprised person you'll ever see."

Mitchell said he has talked to 12 other GHA physicians yesterday, all of whom said they would support a strike. Mitchell said that GHA physicians would still treat emergency patients and would not abandon hospitalized patients.

Unlike commercial health insurance plans, GHA collects a premium from its members and supplies them with necessary hospital and medical care rather than having the members seek their own private physicians. GHA's physicians are salaried employes of the plan and do not receive a fee for their services. the governing board of trustees of GHA is elected by the plan's membership.

The three issues still not settled concern the adequacy of malpractice insurance for physicians under a self-insurance program the board wishes to adop, continuation of a ban on GHA physicians being employed outside the plan and changing the number of clinic hours for internists and pediatricians from six hours a day and to seven, reducing the hospital round time from two hours to one a day.

Wool noted in an interview that previous contracts with the physicians, who formed their union under National Labor Relations Board procedures in January, had barred full-time GHA physicians from outside work. Wool said GHA was offering a "very liberal compensation package," including a 28 percent increase in pay and benefits.

"In exchange for that, we feel we have a right to expect a full dedicated commitment to our members," Wool said. GHA was foffering "a fair day's pay for a fair day's work," Wool said, adding that agreement had been reached on pay so that "now we have to get agreement on a fair day's work."

That meant, he said, requiring primary physicians to see patients in the clinic seven hours a day and to continue the ban on outside work. Allowing GHA physicians to have an outside practice, Wool said, "will inevitably compete with their ability to serve our patients."

Lieberman, who said that "economics was not an issue" in an interview, asserted at another point that if a physician wanted to work outside GHA, he had a "civil right . . . a God-given right in the United States of America to go out and make more money as a physician."

Wool and GHA's executive director, Louis J. Segadelli, said contingency plans had been made to deal with emergencies and urgent medical problems if the physicians strike. About 55 of GHA's 97 pjhysicians belong to the union.