The Miami riots are another warning.

We did not heed the fire last time. Three days of murderous violence in Miami's Liberty City earlier this month demonstrated all too vividly that ghetto conditions are no better - an in some respects worse -- than they were in the summer of 1967 when 24 inner-city ghettos burned.

In this summer's refun, we again deplore the racial division in American society. We again deplore black poverty, the slums, injustice and the lack of jobs and hope. Again we talk about the need to end those dangerous conditions.

But substantial improvement of the ghetto, I am afraid, is impossible. You cannot improve this plague.

What we should talk about -- and attack with all deliberate speed -- is not ending miserable ghetto conditions, but the ghettos themselves.

Americans have never fully faced the facts. As the Report of the National Advisory Commission on Civil Disorders, better known as the Kerner Commission report, pointed out 12 years ago, there are ultimately only two alternatives to dissolving the ghettos: "blind repression or capitulation to lawlessness." Either would be a threat to every American and destroy basic democratic values.

The only acceptable course, in the words of the Kerner report, is "the realization of common opportunities within a single society."

But if we did not know it, or did not want to know it, in 1968, we should know now that there are no opportunities to realize in our inner-city ghettos.

The inner-city ghettos as we fear them today -- whether in Liberty City in Miami or along the H Street NE corridor in Washington -- devloped in the 1950s and '60s when millions of semilliterate, semiskilled blacks lost their livelihoods to farm mechanization. They crowded into the big cities in search of jobs. The jobs had just left. Industry, along with the white middle class, was leaving the cities.

To get a meaningful job in our new, highly mechanized industry takes education. Effective education, as any teacher will tell you, takes motivation. Motivation takes a dignified living environment that inspires hope and ambition. A dignified living environment takes money. Money takes jobs. The circle is vicious indeed.

We have tried to break the circle with federal subsides. The government poured money into ghetto schools, built ghetto housing and moved factories back into the ghetto. It was never enough.

This is not to disparage many admirable and heartwarming efforts. In America, the extremes of stupidity, callousness and greed are always matched by extremes of intelligence, compassion and generosity. That makes America so American.

No doubt, there is visible and encouraging progress in race relations and equal opportunity. The black airline stewardesses and executives are no longer token.

Affluence has trickled down since the 1967 riots. It has put many black families on the ladder of upward mobility. And they managed to climb out of the ghetto and move to the suburbs.

Eunice and George Grier of the Greater Washington Research Center recently found that, despite continuing discrimination, blacks are moving out of Washington so rapidly that one suburban household in eight is now black. Most have gone to Prince George's County.

But these new suburbanites are almost all young, upwardly mobile families with incomes of $15,000 or more, a high-school education and at least two years of college. The poor and poorly educated remain in the ghetto.

There is no hope that established white suburban communities will accept their "fair share" of the ghetto poor. Nor would it make sense to offer affordable housing to low-income people in areas where they could only work as domestic servants and would need two cars to get around.

In planned communities like Reston and Columbia, however, racial and economic integration has worked remarkably well.

Not that residents in the "new towns" of Reston and Columbia are superior in tolerance or liberalism. But they willingly and often cheerfully accept people poorer and darker than themselves because they know that minorities will remain in the minority.

In a planned community, the privileged will not be overwhelmed by the underprivileged.Property values are not effected. School standards are not lowered by an overly large number of poorly educated children.

The proportion -- call it "the quota," if you must -- that the majority deems acceptable is fixed in the planned community's master plan.

The master plan assures stability. It assures that subsidized housing is built in small clusters throughout the community. Ghettos and a high number of underprivileged students in any one school are thus avoided. The streets and yards of the poor are more readily kept as clean as those of the rich. Garbage is picked up by the same trucks. Both groups share playground and community centers.

Ten years ago, as systematic federal effort to encourage planned and racially and economically integrated communities in America seemed promising. Planned communities were to save us the cost of urban sprawl and enhance the quality of life with good housing, good schools, health care and recreation in close proximity. People would be able to stay put instead of burning a lot of gasoline.

With such planning there might not be any more ghettos today. Under a coherent urban strategy, we would have built low-income housing in outlying communities to bring people and jobs together. The vacated inner-city housing would have been "recycled" for a more affluent market. According to the arithmetic of Bernard Weissbourd, a successful private developer in Chicago working with the Center for the Study of Democratic Institutions, we could have created a housing surplus which in turn might have achieved a fairly even distribution of black and white throughout metropolitan areas.

Unfortunately a national policy of new-town development and regional planning, which Congress called for in 1970, was never carried out. Lengthy studies have been written to explain how and why the 15 government assisted new towns floundered. the reasons are complex. but in the end they all boil down to one fact: The Nixon administration did not want the program to work. d

With the added imperative of saving energy, it is time to revive some sort of urban strategy. Perhaps we are a little smarter now. A renewed effort to build planned communities would not attemtp the hubris of launching new cities from scratch. We would enlarge existing small towns. There is also a greater inclination to revive the old city centers.

Americans are not longer frightened that planning will bring about regimentation. We all see that in the suburbs or in the ghettos, it is nonplanning that limits our choices and our freedom to live as we please without fear. What scares Americans about national planning, regional planning and planned communities is the fear that government will bungle it and that it will cost a loss of money.

The former is a matter of citizen participation and education, of careful public control. It is not easy.

As to cost, it is far less expensive to build a good environment than a bad one. We can, in fact, no longer afford to make environmental mistakes.

The fire next time could wreck more than Liberty City.