The U.S. Commission on Civil Rights yesterday called busing between cities and suburbs the only viable way of desegrating public schools in the nation's large urban areas.

"We have concluded that metropolitan school desegregation is a must if the constitutional rights of today's children and young people to equal opportunity are to be upheld," commission chairman Arthur S. Flemming told a news conference.

Declaring the large urban centers of the North and the West to be increasingly isolated along racial and economic lines, the commission said: "We have come to the point where substantial integration of public schools can be accomplished only if the area covered is larger than the city itself.

"Plans in big cities that provide for intradistrict desegregation are not likely to remain stable whatever the level of minority enrollment in the system . . . For these children, racially isolated education will continue to be a reality for the foreseeable future."

The commission, a federal agency that monitors civil rights progress, has no authority to order remedies but many of its recommendations have become law.

The commission criticized a common contention that school desegregation should be eliminated by ending housing discrimination and neighborhood segregation. Commission members said that could take years and in the meantime many children are being denied their rights.

The commission noted that city suburban desegregation plans have been put into effect in such places as louisvill-Jefferson County, Ky.; Charlotte-Mecklenburg County, N.C., and Nashville-Davidson County, Tenn., and that those remedies have proved to be stable.

But in each case a single school district operated city and suburban schools, whereas in most Northern and Western areas city and suburban school systems are separate entities, the report said.

Nevertheless, the commission added, most states have the authority to desegregate schools on a metropolitan-wide basis and in most cases it would not be necessary to cross state lines. The one exception mentioned was Washington, D.C., whose perdominantly black schools are surrounded by suburban systems in Maryland and Virginia.

Since the Supreme Court's 1954 decision outlawing school segregation, the commission said, blacks and other minorities have been concentrated in cities in increasing numbers while whites have fled to the suburbs.

Thus, while at the national level 40 per cent of the black school-children attend schools 90 per cent more black, in the nation's 26 largest cities that figure is 75 per cent, the commission said in its report, issued yesterday.

By 1974, 20 years after the original decision on desegregation, the nation's five largest school systems - New York, Chicago, Los Angeles, Philadelphia and Detroit - were all more than 50 per cent minority, the report noted. In Chicago and Detroit, the minority enrollment was more than 70 per cent, while in New York and Philadelphia it was more than 60 per cent, it said.

While the commission called for voluntary desegregation measures on a metropolitan-wide basis and criticized the federal government for what it called a lack of leadership in the desegregation area, it also expressed confidence that the courts will eventually order metropolitan desegregation.

It said that the concentration of blacks in cities "has come about because of the discriminatory practices of important insitutions in our society which government has tolerated, fostered and in some instances mandated." Proof of such practices in court, the commission said, could become the basis for an order directing metropolitan desegregation.

Pending in the federal courts are two cases, Wilmington and Indianapolis, where busing has been ordered across district lines to achieve desegregation. In a 1974 case involving Detroit and its suburbs, the Supreme Court declined to order city-suburban busing, holding that it had not been shown that the suburbs had contributed to school segregation. The metropolitan aspects of that case are dormant now.

In the Wilmington case, courts have ordered busing between the 88 per cent black Wilmington schools and the 95 per cent white schools in surrounding New Castle County. The decision was based on a 1968 Deleware law permitting the state board of Education to reorganize school districts and redraw boundaries but ecplicity excluding Wilmington from any reorganization.

The Supreme Court has twice refused to set that order aside and the case is now pending before the Third U.S. Circut Court of Appeals on technical aspects of the busing plan.

In the Indianapolis case, busing was ordered across districts lines after an appeals court found a constitutional violation in an Indiana law that establishe a form of metropolitan government in the Indianapolis area but left school boundaries untouch. The case came before the Supreme Court but was sent back for hearings on the segregative intent of the law.

Also penoing is an American Civil Liberties Uniuon suit seeking metropolitan desegregation in Atlanta. The case has not yet come to trial.