About 1,600 low-income families who use subsidized housing vouchers might soon have to pay more for their rent or find a cheaper place to live, and the waiting list for the voucher program will not be opened this year to additional families, according to county housing officials.

Under new federal rules, the U.S. Department of Housing and Urban Development is applying a strict cap to the amount of money that it distributes to local housing agencies for the voucher program, which funds the gap between the cost of housing and the financial resources of the elderly, disabled and working poor. Families in the program typically pay about 30 percent of their income toward rent, and the federal government picks up the rest of the cost.

Advocates for low-income families have criticized the new federal rules, saying they don't allow flexibility if rents rise above inflation, which has been typical in recent years, and limit access to the program. Previously, the federal government had set rent limits for every community and then reimbursed the costs.

William Murphy, rental assistance director for Montgomery's Housing Opportunities Commission, said the agency estimates that it will have to reduce subsidies to about 1,600 of the 5,600 families that have housing vouchers. The size of the cuts will vary based on several factors, such as a family's size.

"Any increase in the burden on them is going to be unbelievably difficult," Murphy said. "Many of the families are elderly and disabled and they're on fixed incomes."

Under the new rules, Montgomery County is being allowed this fiscal year to spend a maximum of $938 per month per family, up to a total of $60 million.

The median rent for a two-bedroom apartment in Montgomery County, $1,218, is out of reach for 46 percent of the county's renters, according to the Maryland Center for Community Development, a Baltimore-based housing and community development advocacy group. To afford that apartment, the group estimates, a person who makes the minimum wage would need to work 182 hours per week.

In August, when the Housing Opportunities Commission opened its waiting list for the rental assistance voucher program, nearly 10,000 residents applied over a five-day period. Typically, the commission has been able to give vouchers to just 100 to 200 new families a year, Murphy said.

Federal housing officials have said that the changes to the voucher program are necessary to constrain the program's rapid growth, which they say is expensive and takes money away from other government initiatives.

But local housing advocates worry that any cuts in such programs will intensify the county's crisis in affordable housing. Housing costs have risen each year, and developers and landlords find it increasingly easier to build and rent to higher-income families.

Kelley O'Dell, associate director of the county's Coalition for the Homeless, said many people who don't have a place to live are longtime Montgomery County residents who have been priced out of the housing market. She worries that the cuts in the housing voucher program might cause more people to become homeless.

"Many people who are eligible for vouchers just can't get them," she said. "If HOC has to take steps, it will definitely make a difference. They have several choices to make, and none of them are good ones."