Federal Reserve Chairman Alan Greenspan is expected to push the Senate to create a powerful new federal body to oversee Fannie Mae and Freddie Mac in Congressional testimony this week that will mark his most forceful call to date for new regulations for the federal housing giants.

Greenspan is well-known for his support of stricter rules for Freddie and Fannie, but his testimony before the Senate Banking, Housing and Urban Affairs Committee on Tuesday is expected to be the first time that he has clearly laid out his vision.

In doing so, Greenspan hopes to provide new momentum to Congressional efforts to strengthen the oversight of Fannie Mae, Freddie Mac and other government-sponsored entities, or GSEs.

“He wants to push the process along,” said Bert Ely, a critic of Fannie and Freddie. “He may feel that he needs to put another stick of dynamite underneath it to move it along.”

Sources close to the matter say that Greenspan will issue only a general call for a new regulatory body with vast new powers to oversee Fannie and Freddie — and will not get bogged down in details about the scope of the new regulator.

“He’s going to call for a new regulator and leave it open,” said one lobbyist working on the issue.

Greenspan’s comments are expected to give a boost to efforts by Banking Chairman Richard Shelby (R-Ala.) and ranking member Paul Sarbanes (D-Md.) to draft legislation this year to create an independent agency to oversee GSEs.

However, it is far from certain that tough legislation could pass either chamber.

Last year, House Financial Services Chairman Mike Oxley (R-Ohio) showed how difficult it is to move legislation on Freddie and Fannie when he was forced to call off a committee vote on his version of the legislation just hours before it was scheduled to begin.

Working with his ranking member, Rep. Barney Frank (D-Mass.), and Rep. Richard Baker (R-La.), Oxley had prepared legislation that would transfer authorization over Freddie and Fannie to the Treasury Department from the Office of Federal Housing Enterprise Oversight.

As the hearing approached, Oxley secured the support of the Bush administration — as well as Fannie and Freddie — and most of the committee members.

But the night before the markup, White House Chief of Staff Andy Card called Oxley to withdraw the administration’s support and ask for Oxley to call off the committee vote.

A frustrated Oxley canceled the vote and decided to wait and see what his Senate counterparts come up with.

The Senate Banking panel’s hearings on Tuesday and Wednesday are the chamber’s first step toward putting together a bill.

Most lawmakers agree that Freddie and Fannie should be subjected to new federal regulations, particularly after Freddie Mac acknowledged last year that it underreported its earnings by $5 billion.

However, there is little agreement over important details of a new regulator.

Even Freddie and Fannie are prepared to accept new oversight, but they are opposed to overly restrictive rules that, for example, would require the GSEs to get federal approval before rolling out new housing finance products.

“Fannie and Freddie are ready to accept a regulator. The question is: What are the things that the regulator is allowed to regulate?” asked one lobbyist for the GSEs.

Congressional Democrats also worry that the new regulator will focus on the financial elements of Fannie and Freddie, while ignoring the goals of advancing homeownership.

During this week’s hearings, much of the attention is expected to focus on a controversial study published by the Federal Reserve in December which charged that the housing GSEs lower mortgage rates by only a tiny amount.

The report found that the existence of Freddie and Fannie help to lower mortgage rates by about 0.07 percent.

Fannie Mae and Freddie Mac have spent much of the past month undermining the report, a campaign they plan to take right to the chairman of the Federal Reserve when he comes to Capitol Hill.

Last week, Fannie Mae released its own study performed by New York University business school professor William Greene that called into question key parts of the Fed report.

“I conclude that the results in the study may well be seriously flawed and should be subject to extensive scrutiny,” Greene wrote in his report.