RTC May Alter CD Rate Rules for Failed S&Ls; : Thrifts: Savers would be able to lock in high rates for at least three months after a takeover.

Savers at failed thrifts may be able to keep their high rates on certificates of deposit longer.

The federal Resolution Trust Corp. may soon change a policy that has permitted banks and other purchasers of insolvent thrifts to repudiate rates on CDs two weeks after taking over the institutions, officials said Wednesday.

Many CD holders were negatively affected when the RTC--the agency overseeing the thrift bailout--adopted the controversial policy last year. In most cases, rates were replaced by lower ones. That hurt savers who had bought CDs at troubled thrifts because rates were higher.

On May 16, the RTC staff will recommend a rule change that would require thrift acquirers to maintain the thrifts’ CD rates for at least three months, officials said. The change is expected to be adopted by the RTC board.

Alan Whitney, a spokesman for RTC Chairman L. William Seidman, said Seidman believes the change will provide more stability in the money market.

Large depositors will be assured that their rates will be locked in for at least 90 days after a thrift is sold, Whitney said. That will enable them to compare CD rates to those of 90-day Treasury instruments. With such stability assured, troubled thrifts may not have to offer extremely high rates to attract depositors.

In addition, the rule change will allow buyers of failed S&Ls; to estimate more precisely their cost of obtaining deposit funds following the purchases, Whitney said.