A tax-free bond program that provided below-market financing to build Goldman Sachs Group Inc.'s headquarters is expiring while New York developers say the city's commercial real estate market still needs support. Congress created the Liberty Bond program in March 2002 with $8 billion in tax-exempt funds to rebuild lower Manhattan after the Sept. 11 terrorist attacks. The allocation ran out last month, and the tax exemption ended on Dec. 31 along with dozens of other breaks for manufacturers, energy companies and transit commuters. Critics that include affordable housing advocates say the bonds were little more than a subsidy for fancy Manhattan apartments and office towers for Goldman Sachs and Bank of America Corp. Developers counter that, more than a decade after the attacks, low-cost financing remains necessary to help lower Manhattan's commercial market recover. The Liberty Bonds made available to the World Trade Center site are only enough to support rebuilding a little less than 60 percent of the office space lost on 9/11," Larry Silverstein, the World Trade Center's developer, said in an e- mail. "In an ideal world, more such resources would be made available to help jump-start construction of the remaining 40 percent of the office space that was destroyed by terrorists." His company, Silverstein Properties Inc., received almost $3 billion through the Liberty Bond program to help redevelop the World Trade Center site. Goldman financed construction of its headquarters at 200 West St. with about $1.5 billion in Liberty Bond financing. Bank of America's tower across from Bryant Park was financed with $650 million in Liberty Bonds.