Fannie Mae is expected to announce Friday that it is scrapping a policy requiring higher down payments on home mortgages in areas where house prices are falling.

The change comes in response to protests from vital political allies of the government-sponsored provider of funding for mortgages, including the National Association of Realtors, the National Association of Home Builders and organizations that promote affordable housing for low-income people.

Those various groups have said the policy is hurting an already feeble housing market by shutting out too many potential buyers.

The current policy, adopted in December and now due to end June 1, limits loan amounts in areas with declining home prices, including most of the densely populated parts of the country.

For instance, if a loan program normally allows people to borrow up to 100% of the estimated property value, the maximum is cut to 95% in "declining markets."

Under the new policy that is taking effect next month, Fannie will have the same maximum loan percentages across the country for people purchasing single-family homes that they intend to occupy, according to people familiar with the plan.

For borrowers approved by Fannie's automated underwriting program, the maximum generally will be 97%. For those approved by other means, the maximum will be 95%. (Fannie also has some loan programs, typically offered through state or local housing agencies or nonprofit groups, that allow certain borrowers to make no down payment.)

Fannie is expected to continue to have variable down-payment requirements on mortgages considered riskier, such as those used to buy investment or vacation homes.

Fannie and its main rival, Freddie Mac, own or guarantee the bulk of U.S. home mortgages and so set nationwide standards for lenders. Freddie also has a policy requiring higher down payments in declining markets. But Freddie earlier this month said it wouldn't require lenders to drop below 95% of the estimated value.

In a letter to the Realtors last week, Freddie also said that it is applying the policy flexibly. For instance, if appraisers can demonstrate that home prices in a given neighborhood are stable or rising even though values are falling in the wider metropolitan area, the declining-markets policy doesn't apply.

By softening the down-payment policies, Fannie and Freddie are taking more risks.

Borrowers who put just 3% to 5% down in many areas are likely to find within a year that they owe more than the homes are worth because prices have fallen, a situation known as being underwater.

In some cases, deeply underwater borrowers are choosing to walk away from their homes rather than trying to find a way to keep on paying, Patricia Cook, Freddie's chief business officer, told analysts this week.

But Fannie officials have argued that they have tightened lending standards in other ways -- for instance, insisting on higher credit scores for people who make small down payments -- to reduce default risk. Officials have also argued that underwater borrowers don't necessarily choose to walk away.

The concessions from Fannie and Freddie illustrate the conflicting pressures that they are facing. Many critics say they are taking far too many risks, increasing the danger that taxpayers may end up having to bail them out.

But politicians and the housing industry are pushing them to do more to prop up the housing market.

In a recent letter sent to Fannie and Freddie, the Realtors reminded the companies that the trade group in recent years helped them fend off Bush administration attempts to impose tighter regulatory constraints.

Fannie and Freddie may need the Realtors' lobbying support in the weeks ahead as Congress seeks to give final approval to long stalled legislation designed to improve regulation of the two companies.

Write to James R. Hagerty at bob.hagerty@wsj.com

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