Prince George's County Executive Parris N. Glendening said yesterday that he is considering layoffs of police officers and firefighters to reduce an estimated $72.5 million budget shortfall.

Glendening's position marked a dramatic reversal of earlier public assertions that police and firefighters would not be dismissed to help balance the budget. Cuts are also possible in the county's support of the schools, Glendening said.

"What we have indicated is that we're looking right now at all options," Glendening said. "Education and public safety have always been our highest priority, but we have a very serious situation in which you cannot exempt close to 70 percent of your total budget from any cuts."

Glendening said he was referring only to the current budget when he said that he would exempt police and firefighters from layoffs. Increasing revenue shortfalls for fiscal 1992 have forced him to "consider all options, across the board," he said.

The county projects that it will carry a $40 million to $50 million deficit from this year into the $1 billion budget for fiscal 1992, Glendening said. County officials have attributed the revenue shortfall to a regionwide recession, particularly in the real estate market, and on spending cuts by the state.

Glendening said he has asked representatives of the police and other unions to consider forgoing a pending pay raise negotiated in 1989. That raise totals about 12 percent, including cost-of-living allowances and merit pay, Glendening said.

Darryl A. Jones Sr., president of the Fraternal Order of Police Lodge 89, said yesterday the union is "adamantly opposed to the layoffs" and that it also opposes a pay cut. Several union members likened Glendening's talk of layoffs to "economic blackmail," and said they see it as a "thinly veiled attempt" to force officers to accept a pay cut.

"The message from the rank and file has been that they're not inclined to abandon their pay increase," Jones said. "We fought long and hard to get the commitment to hire 400 new officers and the battle to keep them . . . will be even more intense."

Glendening said, "I'm not threatening anyone . . . but collectively, across the board, county employees are looking at a . . . 12.2 percent total pay raise and what we're saying is that if that expenditure or some significant portion of that expenditure is not reduced, we have to make the reductions elsewhere."

Police Chief David B. Mitchell said that he is preparing to work with the county executive to "minimize the impact of any actions on the department."

In August, two weeks before the Democratic primary, Glendening said he planned to increase the force to 1,400 officers by the end of June.

Less than a month later, Glendening announced that he was suspending a hiring campaign to add 200 officers. The County Council had voted in 1989 to add 400 officers over two years after it was reported that the department was so severely understaffed that on many nights as few as 51 officers were patrolling the county of more than 700,000 residents.

As the county's economic situation worsened, Glendening announced in November that 190 county employees, including several civilian employees of the police department, would lose their jobs by mid-January.