The Obama administration announced plans Thursday to beef up a program that reduces the cost of loans that local housing authorities grant to builders that construct and renovate apartment buildings that cater to low-income people.

The Treasury Department is joining the Federal Housing Administration to help finance the 22-year-old program, which enables participating housing authorities to share the risk of the loans with the federal program. By having both Treasury and the FHA inject federal dollars into the program, the housing authorities would get about $500 millon to $1 billion a year vs. the roughly $363 million that the FHA doled out last year.

In remarks at a Washington event Thursday, Treasury Secretary Jack Lew said the initiative aims to “make sure that families who do not want to buy a home or cannot afford to buy a home have access to affordable rental housing.” The administration has long maintained that the nation is suffering from a severe rental affordability crisis.

Lew used the event to also announce that the administration would extend its foreclosure prevention initiatives — including the Home Affordable Modification Program — for another year. That program, which was to expire at the end of 2015, aims to lower the monthly mortgage payments of struggling borrowers. It has reduced the payments of about 1.3 million homeowners, far short of its initial 4 million projection.

Lew also touched on the administration’s effort to lure the private sector back to the mortgage market, which is now largely supported by the FHA, Fannie Mae and Freddie Mac. The administration has been pushing to scale back the government’s role, and Lew said he has directed his staff to bring together mortgage investors and other stakeholders in the months ahead “so we can uncover new paths to increase private investment.”

As for the bid to expand affordable rental options, the New York City Housing Development Corp. will be the first housing authority to benefit under this initiative when it receives funds to help rehabilitate rental housing in Far Rockaway, Queens, that was damaged by Hurricane Sandy, Lew said.

The program allows local housing authorities to underwrite loans backed by the FHA that fund affordable apartment rentals. The housing authorities share the risk of any losses on those loans with Treasury and the FHA. The administration has repeatedly asked Congress to allow Ginnie Mae to pool these loans and sell them to investors as securities, the way it does most FHA mortgages. Doing so would reduce the cost of financing rental developments, the administration said. But Congress has not taken action, which is why Treasury intervened.

Treasury has directed the Federal Financing Bank to inject money into the program alongside the FHA. The bank, created by Congress, is a government corporation supervised by Treasury that is supposed to help federal agencies finance programs at the lowest cost to taxpayers, administration officials said.