Mayor Bloomberg and Gov. Pataki joined HUD Secretary Mel Martinez downtown to announce the added subsidy to developers who agree to set aside 20 percent of their units for families earning $50,000 to $80,000.

Bloomberg said the measure would result in 315 apartments for middle-income New Yorkers.

Jerilyn Perine, the city's housing commissioner, said the $50 million inducement, part of the federal funds held by the Lower Manhattan Development Corp., was needed because tax-free federal financing offered to developers in the area isn't enough to "get them to incorporate the low-income requirement."

Bettina Damiani of Good Jobs New York cautioned that the affordable units represent just a fraction of the market-rate apartments on tap for lower Manhattan.

HUD said 398 units have been approved for federal financing, with 5,000 more in the pipeline.

David Seifman