The Loudoun County Board of Supervisors has taken initial steps to constrain increases in next year's county budget and has declined to commit money to a private foundation seeking public funds for low-cost housing.

Three months after approving a $273 million budget for the fiscal year that began July 1, the board on Tuesday asked County Administrator Philip A. Bolen to produce a list of possible "cost containment" measures for consideration in September.

Among them could be a limit on the rate of increase of the next budget, officials said. The current budget represents a 30 percent increase over the previous year's, and Bolen said he could not rule out the need to make new cuts in the current budget and limit spending in fiscal 1992.

County officials may need to sit down with the School Board and other agencies and say, "Folks, it's bad," said Board of Supervisors Chairman Betty W. Tatum (D-Guilford). "We're going to have to cut back; we're going to have to watch every penny," she said.

Tatum and others said their concerns are prompted by the poor state of the nationwide and local economies, the shakiness of many financial institutions, rising oil prices, federal cutbacks on defense spending, an expected leveling off of Loudoun real estate taxes attributable to a flattening of assessments and the likelihood of new state budget cuts.

Supervisor Betsey Brown (D-Catoctin) said she favors deciding by December on the maximum budget increase the supervisors will approve next spring for fiscal 1992.

Earlier Tuesday, representatives of the newly formed Loudoun Foundation for Adequate Housing asked the Board of Supervisors to give it $60,000 to help underwrite its operating costs through December. The supervisors asked the county attorney and other staff members to look into how the county might assist the foundation, but made no funding commitment.

The foundation is an outgrowth of the county's Affordable Housing Advisory Committee and is similarly urging that the county take an active stance in assuring that some houses built in Loudoun be within the reach of first-time buyers who are paid less than the median income.

Developer Robert DeLuca, vice president of the new foundation, has provided an unspecified amount of start-up money to the organization, which recently hired an executive director. The foundation proposes to own, manage and develop low-cost housing, possibly using cash and other assets pledged by local developers in the rezoning process. The county government may provide expedited review to two low-cost housing demonstration projects planned by developers. However, some supervisors have indicated reluctance to trade increased density for lower home prices.