The Montgomery County Zoning Appeals Board has delayed a decision on a controversial proposal to build an ambulatory-care facility for staff physicians at Bethesda's Suburban Hospital, after hospital officials told the board that financing for the project is in doubt.

The request for a special exception to build the ambulatory-care facility will now be heard in January 1987.

The plan calls for a five-story medical office building and a 475-space underground garage on land adjacent to the hospital and across from the National Institutes of Health on Old Georgetown Road. Nearby residents oppose it as being "too massive" for the neighborhood of single-family homes.

Hospital Administrator Lynn Frank said Suburban asked for the delay because a bill before Congress would deny tax-exempt financing to hospitals.

Frank said the bond market "has been flooded with requests for tax-exempt financing" since developers learned of the proposed bill, which is known as Treasury Two. "We were just not far enough along with our proposal to float our bonds, nor could we be guaranteed we'd get the money if the bill passes this session," he said.

Frank said the cost of the proposed $7 million underground parking lot would be "astronomical under conventional" financing, but the hospital will use the next year to explore these methods, as well as a less costly version of the underground garage in case its tax-exempt status is eliminated by the pending legislation.

Members of the community who fought the expansion for nearly two years are "ecstatic" about the Oct. 17 postponement, according to Spring Swinehart, president of the Huntington Terrace Citizens Association.

"We're thrilled. We feel they asked for the continuance not just because they lost their financing but because both the planning staff and the planning board had recommended denying the zoning exception. Hopefully, they'll scale down the proposal before the 1987 hearing," she said.

Any changes made to the current Suburban proposal must be finalized and submitted to the zoning appeals board and the civic association 90 days before the hearing, zoning officials said.