More than 600 architects and artists, including I.M. Pei, Saul Steinberg and Isamu Noguchi, have sent a petition to New York's Whitney Museum of American Art to protest plans for a museum addition they believe will "totally destroy the architectural integrity of the original building."

The petition is the latest round in esthetic arm-wrestling that began earlier this year when the Whitney unveiled a design by Princeton architect Michael Graves that would substantially alter the austere facade completed by the master modernist architect Marcel Breuer in 1966.

The signers are calling themselves the "Ad Hoc Committee to Save the Whitney," and while their protest is genteel, by and large, there is no shortage of passion behind it, just as there are few shrinking violets among Graves' supporters.

"It's really grotesque," said Washington's Peter Blake, a petition signer and chairman of the architecture department at Catholic University. "It's an absurd sort of pastry concoction, extremely hostile. It really looks like . . . I don't know what it looks like. The most revealing thing about it is that when you turn it upside down it looks like a big dumb grin."

That "grin" is a large crescent-shaped window along the top of the new addition that would stretch from one end of the museum's facade to another -- just one element of a design that critics describe in tones usually reserved for last week's fish.

Defenders of the design, while not yet petitioning, are no less forthright. They say the $37.5 million addition, which more than doubles the museum's space, humanizes a building that snubs its surroundings.

"Fundamentally, the issue is the city," said Vincent Scully, professor of art history at Yale. "In a sense, the modernists never valued the traditional city. Like so many of the Bauhaus architects, Breuer despised the street," Scully said. "The Breuer design hates everything around it. What Graves does is open the building to the whole neighborhood.

"He believes in the street and the buildings around the museum. He's not trying to make something that is completely aloof."

In a sense the architectural pie-throwing of the great Whitney debate began in the mid-'70s, when an upstart school of architects known as post-Modernists began to challenge the sleek, austere, sometimes boxy style (which reached its nadir, some say, along Washington's K Street) that has dominated American architecture for much of this century. Instead, they began moving toward a more traditional, less forbidding style that featured less glass, more facade and fanciful allusions to classical architecture.

Graves is no stranger to this debate. His design for a municipal building in Portland, Ore., split the city's architects into two camps. His design for the Louisville headquarters of Humana Inc. was similarly provocative.

The design for the Whitney would envelop the present museum, a sleek box of dark stone whose facade cantilevers up and over Madison Avenue, each floor of the building protruding slightly more than the one below it. It uses several different colors in its facade and features windows and layers of stone in a style that some critics have compared to an Egyptian tomb.

Not all of the design's critics are so caustic, but most of them agree that the Graves design has no business on top of the Breuer.

"I think we want to very politely and very moderately ask them to reconsider," said New York architect Ed Barnes.

"We feel about it the same way artists might feel if someone said, 'Let's cut up this Rembrandt and put it into a new collage,' " said another New York architect.

"This is not meant as an opposition to the Whitney or Mr. Graves," agreed Abraham Geller, a New York architect who started the ruckus in June when he criticized the Graves design in a speech at an architectural awards ceremony in New York.

"I have a high regard for Mr. Graves," Geller said, "but unfortunately at times the most talented people -- Frank Lloyd Wright, Le Corbusier -- become myopic in their vision. In this example I think more respect should be paid to the great work that Breuer did. Put it this way," Geller said, "Graves should know better."

Graves could not be reached for comment, but a spokeswoman for the Whitney said the museum board can be expected to stand by its plan. "The Whitney hired Graves to come up with this design and it was accepted unanimously by the board. There's always opposition to everything. These people perhaps have been a little more vociferous."