The Obama administration plans to push forward this spring with efforts to wind down government-backed housing giants Fannie Mae and Freddie Mac and attract more private funding to mortgage markets, Treasury Secretary Timothy F. Geithner said Thursday.

Geithner told reporters that administration officials have begun more intensively exploring legislative options for overhauling the nation’s housing finance system with lawmakers on Capitol Hill, as well as with academics and outside advocacy groups.

Still, he said that concrete changes won’t come soon.

“It’s going to be a complicated process,” Geithner said. “We don’t expect to legislate this year.”

Since the financial crisis, the country’s housing finance system has relied almost exclusively on federal support for funding new home loans. In a white paper last February, the administration outlined three options for a long-term overhaul of the housing market.

Each of those proposals retained the Federal Housing Administration, which focuses on loans to borrowers who can’t afford sizable down payments. Each option also proposed the elimination of Fannie and Freddie but offered different approaches on how — or whether — to replace them.

Republicans in Congress also have advocated shutting down the taxpayer-backed mortgage giants but generally on a faster timetable than the administration has proposed.

“We’re in a much earlier stage on housing reform” than with some other financial regulatory changes, Geithner said. But he added: “What we’re going to try to do is lay the foundation for consensus.”

In the meantime, he said, “Our immediate obligation is to repair the damage to homeowners, the housing market and neighborhoods caused by the crisis.” He referenced new measures proposed by President Obama this week that would make it easier for struggling homeowners to take advantage of record-low interest rates in order to lower their monthly mortgage payments.

Geithner on Thursday also said that the administration has made significant progress in implementing key elements of the financial overhaul legislation passed in 2010 — from creating a new consumer watchdog bureau to imposing tighter risk limits on big financial firms — and rejected GOP claims that the new regulations have overburdened banks and created paralyzing uncertainty in markets.

“We are taking the necessary time to get the substance right,” Geithner said. “This is a critical year for financial reform. . . . We still have a lot of hard and complicated work ahead of us.”