The Federal Home Loan Bank Board has proposed permitting District savings institutions to establish branches in Maryland or Virginia and to allow federally chartered thrifts in those two states to set up branches in the city.

The regulations will be voted on after a 30-day comment period. Little opposition is expected to the proposal. Interstate branching would fulfill a longstanding dream of depository institutions here to expand into the wealthy suburbs. In the years of frustrated waiting, the number of District thrifts has diminished by half, to seven.

The proposed rules mark the first time the agency has made an exception to its policy against interstate branching. A number of interstate acquisitions have been permitted in recent years, but all of them have involved takeovers of troubled institutions. There is no such requirement of financial hardship in this proposal, nor is there a limit on the number of branches a thrift could open in the state it chooses.

The rules would permit D.C. institutions to choose Virginia or Maryland; they could not enter both. It would not allow Virginia thrifts to go into Maryland or Maryland institutions into Virginia.

Commercial banks here have just recently been granted the authority to undertake mergers and acquisitions of out-of-state institutions through regional compacts. Several transactions already have been announced.

A few area savings and loans already have a presence in two or more of the three jurisdictions, thanks to acquisitions made many years ago before the policy against interstate activities was instituted. Those could continue.

Perpetual American Federal Savings Bank, once based in the District, had a number of offices in Maryland before acquiring a troubled institution in Virginia in 1982 and moving its headquarters there.

Columbia First Savings and Loan long has had an office in Maryland and recently acquired Family Savings & Loan of Springfield.

National Permanent Federal Savings Bank also has an office in Maryland. It would be permitted under the proposal to establish branches in Virginia as well.

In proposing the rules, the agency recognized the geographical uniqueness of the District. In no other area does the board restrict branching activities to a single city.

Besides ending this anomaly, the board declared interstate branching also would "serve the convenience and needs of consumers in the District, Maryland and Virginia without harming existing institutions in those jurisdictions." The regulators also feel the action would increase competition in the area, reinvigorate District thrifts -- most of which have been having trouble -- and reduce the risk to the Federal Savings and Loan Insurance Corp.

Of the seven District thrifts, only two -- Washington Federal Savings and Loan and OBA Federal Savings and Loan -- operated in the black last year. Although figures are not yet available for 1985, it is believed that the decrease in interest rates has aided District thrifts as well.