The Carter administration is leaning toward a proposal that would allow bank holding companies to merge or acquire banks and to engage in electronic banking on a regional basis.

Domestic affairs adviser Stuart Eizenstat outlined the White House position in a private briefing late last week for the leadership conference of the American Bankers Association.

However, Eizenstat told the bankers, the administration is not yet ready to make a formal proposal to Congress, which in any case is not expected to take up the controversial issue this year. He indicated President Carter would like to meet with representatives of affected banking institutions before the administration issues its final recommendations on the matter. No date was set for the meetings.

Under the McFadden Act, banks are prohibited from establishing full-service branch offices across state lines. The Douglas Amendment to the act also prohibits bank holding companies from doing so. It is this amendment and its "antiquated restraints," rather than the act itself, that the administration seeks to phase out.

Part of the administration's go-slow approach -- its banking report was due 10 months ago -- stems from the importance it attributes to the matter. According to those present at last week's private briefing, Eizenstat labeled the possible establishment of interstate bank branches "the transcendent financial reform" of the 1980s. Other reasons for the delay were the need to see the omnibus banking deregulation legislation through Congress and the desire to avoid tackling the emotional issue of interstate banking in an election year.

Although Eizenstat did not specify the nature of the "regions" into which bank holding companies would be allowed to expand, it is generally accepted in the banking community that this refers to so-called natural market areas; e.g., the suburbs around a city. Washington, D.C., and Chevy Chase would fall into this category.

The idea is controversial because it leaves open the possibility that the U.S. banking system will become concentrated in a decreasing number of large regional or national banks at the expense of small, local banks. To some extent this possibility has been foreshadowed by the spread of so-called "edge" corporations, authorized by a revision of banking laws last year. This Edge Act allows bank holding companies to establish offices outside their home states to handle international banking transactions with foreign and domestic clients.

For example, BankAmerica Corp. of San Francisco, the holding company for the country's largest bank, has established a network of edge branch offices in the Bahamas, Miami, New York, Chicago and Houston. Other large holding companies are following suit. It is thought that if the green light is given to interstate branching, these edge offices will be converted as soon as permitted to full service branches, thus giving these companies an edge on the competition.

Copies of the administration's draft report have been circulating for months in banking circles, so the contents proved no surprise to the ABA leaders. But Eizenstat refused to answer any questions about how holding company expansion would be implemented.

After the meeting with Eizenstat, the ABA, whose members are divided on the issue, issued a restrained statement saying: "The question of increasing merger and acquisition activity is only one part of a very broad pattern of possible change. As the general proposals described by Mr. Eizenstat evolve into specifics, they will be considered along with a host of other issues that tie in with them, including a wide range of new powers that banks may need, plus the question of competition from retailers, the insurance companies, pension funds, stock brokerage firms and the like."