American Telephone and Telegraph Co. yesterday redrew the map for local and long distance calling nationwide, outlining 161 regions where local telephone service will be provided by the 22 new operating companies created by the break-up of the Bell System.

All service between or beyond those areas will be left open to competition among AT&T and rival long distance firms.

The plan was defined in a massive set of papers submitted yesterday to U.S. District Court Judge Harold Greene, who is presiding over the breakup of AT&T. If he approves them, they will become part of the radical new structure of telephone service across the nation envisioned in the decree that ended the federal government's antitrust case against AT&T.

The 161 areas -- mostly in urban communities -- will mark the limits of telephone service provided by the local companies that are now AT&T subsidiaries.

Service beyond the 161 areas -- even between Fairfax and Loudoun counties, or Montgomery and Frederick counties -- will be considered long-distance service. Under the terms of the consent decree providing for AT&T's breakup, long distance may not be provided by the companies currently making up the Bell System.

Telephone service within each "local access and transport area," or LATA, will be provided by the company that set it up. But service between LATAs will be provided by competing long-distance telephone companies, such as AT&T's own Long Lines Division or MCI Communications Inc.

Telephone customers seeking service outside the LATA in which they live or do business will have to acquire it from a long-distance company.

Although there is no legal guarantee that any company will offer long-distance service between the LATAs or into the mostly rural areas outside the LATAs, AT&T's Long Lines Division will do so, a company spokesman said yesterday.

The breakup of AT&T's nationwide phone network does not mean rural communities will lose their long-distance phone service, as many lost air service when airlines were deregulated, because AT&T will continue to offer service to the communities it now reaches, the spokesman said.

AT&T provides this long-distance service now. The court decree for AT&T's breakup simply opens long distance to competition and requires the 22 local companies to provide access to their telephones to any long-distance service providers.

Service within the Washington LATA, for example, will be provided by, and billed through, the Chesapeake and Potomac Telephone Companies of Washington, Maryland and Virginia. But service between the Washington LATA and those centered in Baltimore, Hagerstown, Salisbury, Culpeper, Richmond and other LATAs in Virginia will be open to competition, with the local companies providing only mechanical access to long-distance operators.

The Washington LATA will include the District of Columbia, the Maryland counties of Montgomery, Prince George's, Charles and St. Mary's; Fairfax and Arlington counties and Alexandria in Virginia. It excludes Loudoun County, which is in the Culpeper LATA. So telephone users desiring service between Loudoun and Culpeper counties will have to buy it from whichever long-distance telephone companies choose to compete for business there.

The significance of the LATA system does not lie in its immediate impact on rates, AT&T officials said, or in such mechanical questions as which calls require dialing area codes and which do not. The creation of the LATAs defines the areas in which the local companies spun off from Ma Bell can provide comprehensive service, and it opens to full-scale competition the provision of service beyond a LATA's limits.

The LATA system covers only those parts of the country currently served by Bell System companies. Jim G. Kilpatric, an attorney for AT&T, said it is not clear how long-distance service will be provided between the LATAs and those vast stretches of the nation served by independent telephone companies.

Four LATAs serve all of Maryland. About half the land area of Virginia, however, is outside the five C&P LATAs based in Culpeper, Richmond, Lynchburg, Norfolk and Roanoke, and is now served by independent telephone companies such as Continental. These companies throughout the United States have been consulted about linking up with the new Bell spinoffs, Kilpatric said, but "most of them told us they aren't ready to make a decision yet." He said he expected "plenty of response" from the independents during the 30-day period set aside for comment before Judge Greene accepts the LATA system. Implementation of the new long distance setup is expected sometime next year.

In some major cities, the LATAs will affect directly the division of AT&T's assets among the local companies, or the way customers are served, or both. In the New York metropolitan area, for example, the densely populated New Jersey suburbs were included in the New York City LATA, as was Westchester County. This does not mean calls from New Jersey to Manhattan will be billed the same as calls within New York City, but it does mean that the New York Telephone Co., not New Jersey Bell or a long-distance company, runs this lucrative service.

Dallas and Fort Worth, which are now in different area codes, were combined into a single LATA, which means calls between them no longer will be considered long-distance calls.