Representatives of striking nurses and three Prince George's County-owned hospitals reached a tentative agreement last night on 17 disputed positions that have blocked a settlement of the month-long strike, according to a spokeswoman for the nurses.

Donna Hutchinson, strike coordinator for the county staff nurses chapter of the Maryland Nurses Association, said there will be no picket lines today at the three hospitals, pending the outcome of a vote by the nurses at 7 tonight.

Charles Scott, the federal mediator who has directed negotiations since the nurses went on strike Aug. 29, confirmed that a tentative accord was reached when the two sides agreed to submit the issue of the disputed positions to binding arbitration. The final language covering that arbitration process was worked out during negotiations that began at 3 p.m. yesterday, Scott said.

Neither Carolyn Larkin, union president, nor a spokesman for Community Hospital and Health Care Systems Inc., the corporation that runs the hospitals, could be reached for comment.

Union officials have said that about 500 of 650 nurses at Prince George's General Hospital, Greater Laurel-Beltsville Hospital and the Bowie Health Center have been participating in the strike.

A tentative accord on all other issues was reached during a marathon bargaining session that ended about 3 a.m. Saturday. At a scheduled vote on the contract late Saturday afternoon, the nurses gave tacit approval, but decided not to hold a formal ratification vote until the conditions for their returning to work were resolved.

Mike Canning, a hospital corporation spokesman, said at the time that all nurses had been told they could return to work at their same pay levels, but that 22 specialty nursing positions had gone to other persons during the strike. He said the nurses who previously were employed in those posts, primarily in emergency and intensive care units, would be reassigned.

Larkin said seven of the persons hired for the disputed positions were nonstriking nurses and that 15 were newly hired employes.

Canning said the hospital was bound legally by contracts with the persons now filling the positions and that they could not be displaced by returning nurses.

Since the weekend, five nonstriking nurses have told hospital officials that they will not accept the new posts, leaving 17 positions in dispute.

The hospital's offer on other issues, first made on Saturday, includes a 35-cent-an-hour raise retroactive to Aug. 1, to be followed by another 35-cent-an-hour raise in February, and adjustments in weekend and night differentials. Officials said the percentage increase will vary.

The nurses, who now are paid between $17,000 and $25,000 annually, had asked for an 11.5 percent increase.

According to Canning, the newest proposal also provides for the creation of a committee to review the role of professional nurses and allows paid time for nurses who are union representatives to conduct union business.