NEW YORK (AP) _ An artwork of sponges stuck on a canvas sold for more than $21 million Tuesday.

Yves Klein's Archisponge (RE 11) was the top seller at Sotheby's contemporary art auction in Manhattan, a spokeswoman said. But like many other pieces in the auction, it sold below its presale estimate. Many other artworks failed to sell.

Art auctions by Sotheby's and Christie's this month have been held against the backdrop of a gloomy economy that has some observers wondering how many deep-pocketed buyers are left to snap up paintings and sculptures for tens of millions of dollars.

Klein's 1960 work of natural sponges applied to the canvas and executed in the artist's signature International Klein Blue pigment fetched $21.4 million. Its presale estimate was $25 million.

The work is considered by some the most important in Klein's Relief Eponge series. It was included in an exhibition of his work at the Museum Haus Lange in Krefeld, Germany, in 1961, the year before he died.

Tom Wesselmann's Great American Nude (pound)21 sold for $4.1 million, Sotheby's said.

The assemblage art piece, composed of heterogeneous elements, was estimated to sell for $6 million to $8 million. It depicts an undefined figure - save for a Marilyn Monroe smiling mouth - reclining on a bed with a portrait of President John F. Kennedy and a framed picture of the American flag in the background.

The work was censored from a 1963 exhibition at the Washington Gallery of Modern Art. Executed in Wesselmann's trademark red, white and blue, the work is part of his Great American Nude series, described by Sotheby's as "among the quintessential icons of American pop art."

Another pop art work, Half Face with Collar, by Roy Lichtenstein, with a presale estimate of $15 million to $20 million, did not sell.

But a second Liechtenstein work, Study for New York State Mural, sold for $3.9 million, just below its presale estimate. The work is a colorful stained-glasslike painting that was a proposal for a large mural for the Empire State Plaza Art Collection in Albany, New York, that was never realized.

Another highlight included Beggar's Joys, by Philip Guston. Although it sold for $10.2 million and set a record for the artist at auction, Sotheby's said, the sale price fell far below the presale estimate of $15 million. The artist's previous record was $7.3 million, set in 2005 for The Street.

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