Some 3,585 Oahu families who receive rental housing subsidies have been notified that massive federal budget cuts set to kick in Friday could leave them without a roof over their heads.

It’s not yet clear how many federally funded Section 8 rental housing vouchers could be cut — or when the vouchers would be discontinued.

The earliest a family would lose a voucher would probably be May 1, said Pamela Witty-Oakland, city Department of Community Services Director-designate.

"We’re optimistic that something positive is going to happen" to avert the cuts, Witty-Oakland added.

Still, the city sent out a letter to voucher holders last week informing them of the possible cuts so they could start planning for the worst.

The letter, which also went to 1,365 landlords, said "if Section 8 funding decreases, your housing assistance may be terminated."

The so-called federal "sequester" is set to kick in Friday, triggering about $85 billion in cuts to federal spending that White House officials warn will have widespread effects.

What the cuts will mean when they trickle down to Hawaii’s social services programs, though, is still not yet fully known, city and state officials say.

In a statement, state Department of Human Services spokeswoman Kayla Rosenfeld said the agency is "unable to predict the impact of sequestration on its programs and services."

She added, "The DHS is concerned about the impact of sequestration on its clients and programs."

Witty-Oakland said the city’s Section 8 program is at high risk from sequestration because it is entirely federally funded and because all of its vouchers are in use — so there is no buffer in the budget.

Section 8 is open to families whose income does not exceed 50 percent of the median area income. (Most Section 8 families earn 30 percent or less of the median area income.)

For Honolulu, that means a family of four must earn less than $48,950 to qualify.

Under the program, families must spend 30 percent of their gross income on rent and the vouchers cover the rest, up to a ceiling based on the size of the house that the family needs.

The state also runs a Section 8 voucher program, under the Hawaii Public Housing Authority. But HPHA Director Hakim Ouansafi said he does have a little bit of a buffer: Anticipating the cuts, Ouansafi decided to cut back spending last year and not use all of his available vouchers.

About 2,000 families receive Section 8 vouchers through HPHA.

"We should be OK so long as the Congress gets their act together fairly quickly," Ouansafi said.