President Clinton plans to press Congress for $690 million in new housing funds next year to help low-income families defray the cost of rent, White House officials said yesterday.

The request that Clinton will make in his fiscal 2001 budget, which aides are now drafting for public release in a month, would make housing vouchers available to 120,000 families--on top of the 1.7 million families who now receive rent subsidies under the federal government's $9.5 billion voucher program.

People making less than 50 percent of the median income in the metropolitan area where they live are eligible for vouchers, which are distributed by local housing authorities. But three-quarters of the vouchers go to an even needier population--those making only 30 percent of the median income.

The vouchers typically pay 70 percent of the cost of rent in the private housing market, with recipients paying the balance.

If their request is approved, Clinton administration officials said they hope to target a quarter of the new vouchers to particular populations--32,000 families where the breadwinner is moving from welfare to work, and 18,000 to people who are now homeless.

The advantage of vouchers, according to proponents, is that they allow mobility for the poor in a way that public housing complexes do not.

"It's not a building, it's a voucher; the voucher can move you to where the job is," said Housing and Urban Development Secretary Andrew M. Cuomo. "People moving off welfare tend to be in urban areas; the jobs they need tend to be in suburban areas."

Federal housing assistance was among the programs that attracted the most hostility from Republicans when they won control of Congress in 1994. But after several years on the defensive--including four years when the number of vouchers did not grow at all--the Clinton administration has enjoyed considerable success in recent years expanding the Section 8 program under which vouchers are distributed.

In budget showdowns with Congress, the White House in 1998 won funding for 50,000 new vouchers, and, earlier this fall, for an additional 60,000.

From the White House's vantage point, vouchers have gained enough political appeal that the program is one of those Clinton has chosen to highlight in his budget proposal early next year. In what has become an annual ritual, the White House is using the period around the holidays to selectively release parts of its annual budget request--with the idea that these items can draw news coverage during an otherwise quiet stretch.

Cuomo said the political consensus for vouchers as a preferred way of giving help to the poor is strengthening. "You have a president--and a secretary, with all due modesty--who have made it a priority," Cuomo boasted.