LONDON—Despite recent economic turmoil and lackluster auctions results in Hong Kong and London, Sotheby's and Christie's have guaranteed some of the top lots in this week's contemporary art sales. Bloomberg reports that Sotheby's has guaranteed more than half of its total lot value, while Christie's has guaranteed 38 percent.

"I'm concerned about the level of guarantees at these auctions," said London dealer Gerard Faggionato. "I just can't see people wanting to spend £12 million on a work of art at the moment."

Sotheby's, whose contemporary evening sale takes place on October 17, has guaranteed or has a financial interest in 10 works with a combined low estimate of £15.45 million. Among those pieces is Andy Warhol's 10-panel Skulls, with an estimate of £5–7 million, and Gerhard Richter's Jerusalem (low estimate £5 million) and Abstraktes Bild (Rot) (low estimate £3 million).

At Christie's auction, on October 19, Lucio Fontana's Fine di Dio is one of six guaranteed works. Fine di Dio carries a low estimate of £12 million; in June, a pink version of the painting valued at £8 million failed to sell at Christie's. Also carrying a guarantee at this week's Christie's auction is a Francis Bacon portrait of Henrietta Moraes (low estimate £5.5 million).

By contrast, Phillips de Pury & Company has not guaranteed Takashi Murakami's 23-foot-high Tongari-kun sculpture, which leads its October 18 evening sale with a £3.5–4.5 million estimate.

"There's an awful lot riding on these sales in London and next month in New York," said London dealer Alan Hobart. "If they're successful, confidence in the art market will be maintained. If not, people will pull out very quickly."