This weekend, a small group of prominent architects from North and South America is meeting in Washington to scuttle the Charter of Athens and hoist the Charter of Machu-Picchu.

Like the old, the new document is to chart a way out of our environmental problems to a more satisfying urban life for everyone.

At Athens, 45 years ago almost to the day, modern architects charted a pre-dominantly technological approach - high-rise housing projects, freeways, urban dispersal.

At Machu-Picchu, last December, a new generation of architects and planners advocated a more humanistic approach - citizen participation, historic continuity, adapting buildings and settlements to nature and the ecology.

The place of origin of the two statements is significant, say the signers of the Machu-Picchu declaration. Athens, the cradle of Western civilization, represents rationality, as embodied in Aristotle and Plato. Machu-Picchu, the ancient Inca city in Peru (which tood up better than more recent Spanish colonial cities nearby), represents the awareness that humans are part of the natural ecology.

The Charter of Athens came out of a cruise conference of the International Congress of Modern Architecture, better known by its French acronym CIAM, which sailed from Marseilles in August 1933. The congress was dominated by the owlish-looking, Swiss-born French architect Le Corbusier, who used to paint cubist pictures in the morning and practice architecture in the afternoon.

Among the members of CIAM were practically all the now famous architects of the time - Gropius, Mies van der Rohe, Breuer, Aalto and others, along with some historians, like Giedion, and some painters, like Leger.

The 1933 shipboard meeting, with its stopover in Athens, agreed, amidst much frolicking, that due to industrialization, the proliferation of automobiles, rapid urban growth and non-planning, "chaos has entered the city." It laid down rules and planning principles to assure for all citizens equal rights to good housing, health, education, recreation, transportation and job opportunities.

Unlike the Machu-Picchu statement and other architectural manifestos (for which architects seem to have a peculiar predeliction), these rules and principles were never specifically hammered out and signed by the conference participants. Hitler had come to power in Germany. The world was in turmoil. And when the cruise was over everyone hurried home to cast the new wisdom in concrete rather than words.

It was not until 10 years later, in the desolation of Nazi-occupied Paris, that Le Corbusier worked out the charter from his notes and other papers and published it anonymously with a cryptic introduction by Jean Giraudoux, the playwright of "Tiger at the Gates" and "The Madwoman of Chaillot." I suppose Giraudoux wanted to confuse the Gestapo.

In English translation, the charter reached American libraries only in 1973. By that time the planning principles it sets forth had changed urban life around the globe more profoundly than any other architectural concepts since the Renaissance.

Renaissance planning, infatuated with rediscovered Classic grandeur, introduced perspective and, along with the invention of gunpowder, eliminated medieval city walls.

CIAM planning, infatuated with the promise of machine technology, invented high-rise apartment projects - slab-open space-slab - and, along with mass-produced automobiles, exploded the city all over the countryside.

Machine production, however, failed to produce human happiness and social justice. Along with its blessings, it brought pollution, ugliness and a potentially catastrophic misuse of land and natural resources.

Architects and planners are increasingly aware of the shortcomings of the modern credo. Some 10 years ago, the late Greek city planner, Constantinos A. Doxiadis, warned that CIAM planning theories are leading us to commit "great urban crimes." With the help of some of the world's leading intellectuals, such as Barbara Ward, Margaret Mead, Buckminster Fuller, Arnold Toynbee and Marshall McLuhan, Doxiadis - on lovely conference cruises to the Greek islands - tried to develop a new approach to planning human settlements. He called it "ekistics."

The Charter of Machu-Picchu is another effort in the same direction. It is based on a week-long conference held at the National University of Peru in Lima and attended by leading architects and planners from several countries on this hemisphere. They included Felix Candela of Mexico (now teaching at Chicago) and Dorn McGrath Jr., who heads the planning department of George Washington University here.

The Machu-Picchu document reaffirms much that was said by CIAM and praises "the vitality and continuity of the modern movement in architecture and planning." It blames politics rather than planning theory for the "great urban crimes."

"Economic decisions at national and regional levels seldom include direct consideration of city priorities and solutions to urban problems," the charter complains. Besides, the world population has doubled since the Charter of Athens was written, and city populations have grown even faster, causing cities to deteriorate.

Nevertheless, the Machu-Picchu charter finds CIAM wrong in segregating, or zoning cities into different functional components - residential, commercial, industrial, cultural and recreational. Urban vitality, it says, demands integration of people and activities.

The charter calls for less emphasis on individual buildings and motor traffic and more emphasis on community architecture, historic preservation, and "the continuity of urban texture."

The meeting in Washington this weekend of some of the signers of the Machu-Picchu charter will consider ways to continue the discussion in architecture schools here and abroad.

Meanwhile German architects are similarly trying to sort out their thinking. The International Union of Architects, which has given the Machu-Picchu group an honor award, is taking note of these various efforts to update a modernism that is no longer modern.

At its next convention in Mexico next October, the international organization may well make the burial of the Charter of Athens an official, international event.