Responding to housing-industry concerns that tightened mortgage-credit rules would hamstring the critical first-time-buyer market, Fannie Mae and Freddie Mac will offer 3 percent down-payment loans to qualified borrowers.

Fannie's My Community Mortgage program, open to first-time buyers with a 620 minimum credit score, starts this week.

Freddie's Home Possible Advantage, available to all qualified buyers, begins in March.

Andrew Bon Salle, a Fannie Mae executive vice president, said his program's goal was to help qualified borrowers gain access to mortgages, but added that it would not "solve all of the challenges around access to credit."

The announcement Monday by the two government-sponsored agencies sparked concern in some quarters that lowering the credit bar might lead to another housing bubble.

In response, Melvin L. Watt, director of the Federal Housing Finance Agency, which oversees Fannie and Freddie, called the programs a "responsible approach" that will ensure safe and sound lending practices.

Historically, 40 percent of mortgages were underwritten by Fannie and Freddie, but as private credit contracted during the housing downturn and the recession deepened in 2008, the government stepped in, said Philadelphia economist Kevin Gillen.

In the depths of the downturn, about 97 percent of mortgages were issued by Fannie and Freddie, he said. "It's only down to 80 percent," so there are "long-term risks," Gillen added.

The short-term impact "should undoubtedly be positive," he said, and help "underserved households get back in the game."

Realtors are welcoming the programs.

Since first-time buyers usually don't have much cash for a down payment, "it will open up the market," said Nicole Ritchie, of BHHS Fox & Roach Realtors in Media.

Matt Donnelly, of Coldwell Banker Preferred, who sells in Manayunk, said "it will be huge" for first-time, low- and moderate-income buyers, whose purchases "were down a bit this quarter."

Because an FHA loan and its higher insurance won't be the only option, these "buyers could save hundreds of dollars a month in their mortgage payment," Donnelly said.

Robert Acuff, of Re/Max Services in Blue Bell, said it should create interest among first-time buyers "sitting on the fence," especially with interest rates so low, he said.

While welcoming the lower down payment, Patricia Settar, of BHHS Fox & Roach in Mullica Hill, said student-loan debt, with payments as high as $1,000 a month, are as much a deterrent to first-timers.

"If they could refinance that debt to 3 percent, that would be a big help," she said.