Sotheby's and Christie's, the world's leading auctioneers, hold a series of big sales in London over the next two weeks at which the old rivals expect to raise more than 500 million pounds ($800 million).

This time last year the equivalent auctions fetched a combined total of around 425 million pounds, although that was inflated by Sotheby's one-off "Looking Closely" sale that took in a hefty 93.5 million.

Anders Petterson, managing director of the ArtTactic analytical group, said there was quiet confidence that the art market could shake off broader economic blues in 2012.

"Overall the tone is neutral with a positive bias," he told Reuters, summing up the findings of ArtTactic's "Art Market Outlook 2012" report released last week.

"If something really major happens in the (financial) markets then all bets are off, but if things stay as they are we are likely to see a continuation of current levels.

"The auction houses will focus on the very top end and the very rare works of art for which there will be people with the money to buy no matter what's happening on the markets."

After a sharp contraction in late 2008 and throughout 2009 in the wake of the financial crisis, art sales have soared in 2010 and 2011.

Christie's, the world's largest auctioneer, sold art worth 3.6 billion pounds last year, a record in sterling terms. The figure was nine percent higher than 2011, and up 14 percent in dollar terms to $5.7 billion.

Super-wealthy collectors from China have joined the art elite, which now unites established markets like the United States and Europe with relative newcomers from Russia, India, the Middle East and beyond.

Auction houses have tried to focus on high quality paintings and sculptures that rarely, if ever, come to market, and the policy has paid off in recent years.

Although the performance of "blue-chip" artists and ultra-rare works distorts the overall picture of the art market, there is some "trickle down" effect to lower-priced works, experts say.

And with uncertainty surrounding bonds, currencies and stocks, headline-grabbing sums for art are making investors think hard about alternatives.

Booming art demand from China may cool off, however, with recent rapid growth seen as unsustainable in the short term.

Among the London highlights is Christie's "Portrait of Henrietta Moraes," a female nude by Francis Bacon, which is expected to fetch around 18 million pounds ($28 million) on February 14.

The record for the artist stands at $86.3 million set by Sotheby's in New York in 2008 for a triptych.

A week earlier, at its main impressionist, modern and surrealist auction, Christie's hopes to raise between 12 and 18 million pounds for Juan Gris's Cubist still life "Le Livre" and 6-9 million for Joan Miro's "Painting-Poem."

On February 8 at Sotheby's another important Miro goes under the hammer, "Peinture," estimated to be worth 7-10 million pounds and not far off the artist's auction record of $17.1 million set at Christie's in New York in May, 2008.

Several works by Gerhard Richter, both abstract and figurative, feature at Sotheby's contemporary art sale alongside Jean-Michel Basquiat's "Orange Sports Figure" valued at 3-4 million pounds.

Following are the main London art auctions in February.

February 7 - Christie's impressionist and modern art.

February 7 - Christie's Art of the Surreal.

February 8 - Sotheby's impressionist and modern art.

February 14 - Christie's post-war and contemporary art.

February 15 - Sotheby's post-war and contemporary art.

(Reporting by Mike Collett-White, editing by Paul Casciato)

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