The top U.S. housing finance regulator said on Wednesday his agency would unveil a new framework in early 2015 for how government-controlled Fannie Mae and Freddie Mac will set mortgage guarantee fees.

The Federal Housing Finance Agency suspended plans to raise so-called G-fees in January because the agency's new director, Mel Watt, said more study was required.

Watt, who was appointed by President Barack Obama to head the body that oversees the country's largest housing finance firms, has made increasing access to credit a priority and raised fears that higher fees could hurt borrowers.

At a Senate hearing, where Republican lawmakers criticized the decision to delay the fee increases and expressed concern over a new plan to allow lower down payments on government-backed mortgages, Watt defended his more cautious approach.

"To say that we should without a thorough analysis just increase G-fees ... I think was inconsistent with my responsibilities," he told the Senate Banking, Housing and Urban Affairs Committee.

"We expect to provide a framework and the rational for it sometime during the first quarter of this coming year," Watt added, referring to the agency's new vision on fees.

Watt also said Fannie Mae and Freddie Mac, which guarantee most of the nation's mortgages, will release in early December details of the extra requirements borrowers must meet to make a 3 percent down payment on a mortgage.

Fannie Mae and Freddie Mac buy mortgages from lenders and package them into securities on which they guarantee payments of principal and interest. In doing so, they serve as major sources of funding for hundreds of banks. They were bailed out by taxpayers in 2008 during the implosion of the housing market.

At the hearing on Wednesday, Watt also came under criticism from Democratic senators including Elizabeth Warren of Massachusetts, who pressed him to take action to reduce the principal on mortgages of troubled borrowers.

While Watt's predecessor at the FHFA opposed principal reductions, putting him at odds with the White House and many Democrats, Watt declined to stake out a clear position and said the agency was still studying the matter.

"It's just a very difficult issue," Watt said.

"We're going to have an answer... I think we're getting closer."