Commercial and industrial development in Montgomery County will have to halt after current sewer commitments are used up because the county has run out of sewer capacity, officials said yesterday.

County Executive Charles W. Gilchrist said the county could lose new businesses it is seeking in order to broaden its tax base and declared: "This is a high-priority problem. It may be the most pressing matter we have."

Like other Washington area jurisdictions, Montgomerry has been courting commercial and industrial growth to relieve the tax burden on homeowners. That drive, Gilchrist and other county officials say, is jeopardized by the county's worsening sewer predicament.

Frederick T. Agostino, deputy director of economic development, said 1 million to 1 1/2 million square feet of prime office space is in various stages of planning, and not all of it has received sewer commitments from the county.

"It would be unfortunate to lost these opportunities," Agostino said. "We have developed a certain momentum."

According to County Administrator Robert W. Wilson, "all our commecial and industrial sewage share had been allocated. We can't offer any more unless we reallocate other (residential) capacity."

That would require public hearings and approval by the county council.

Gilchrist and Wilson presented their gloomy case at a meetng of the chief elected officials of the jurisdictions using the Blue Plains regional sewage treatment plant.

The meeting had been precipitated by an attempt by the District of Columbia, which is also desperate for more sewer capacity, to take a bigger share of the Blue Plains capacity.

The three-hour session was held behind closed doors. But according to various reports, Prince George's County Executive Lawrence J. Hogan told Mayor Marion Barry that Prince George's would give the city a million gallons of additional capacity -- the equivalent in growth of about 10,000 people -- if the District would drop its court fight to set up a sewage sludge composting facility in Muirkirk between Beltsville and Laurel.

City Administrator Elijah Rogers, speaking for the District at a press conference afterward, declined to say if the city would settle for 1 million gallosn, but he indicated he wasn't happy about the string Hogan attached.

In November, the District said it would take 5 million additional gallons -- although that move was retracted by the Barry administration in a compromise that led to the sewer "summit meeting" that began yesterday.

Regers said, "It is fair to say that all the parties agreed the District needed some relief."

More lower-level talks, then another session involving the top leaders will take place over the next two weeks.

The meetings will cente on one issue: How much surplus capacity does Prince George's have and how much can it give to the District, and possibly Montgomery, without jeopardizing its own long-term needs?

Environmental Potection Agency Regional Administrator Jack J. Schramm indicated that a broad reexamination of Blue Plains would proceed from the talks. Such a reexamination, he said, would include looking at the possibility of letting Blue Plains handle more sewage.