By Chris Michaud

NEW YORK (Reuters) - More than $1 billion worth of fine art, from Picassos and Monets to Rothkos and Richters, will be auctioned at Christie's and Sotheby's in sales that officials say are shaping up to be some of the biggest in years.

The art market, especially at its upper echelons, has thrived as the rich seek a safe haven for their wealth with artworks.

"We had a great rush of consignments for the November auctions," said Marc Porter, Christie's Americas' chairman.

"The property was made up increasingly of discretionary sellers versus estates," he said, referring to collectors who decide to sell a work.

The prices that some of the main items are expected to fetch are eye-popping. Works by Pablo Picasso, Claude Monet and Mark Rothko are each expected to sell for as much as $50 million.

Brooke Lampley, Christie's head of Impressionist and modern art, described it as "an exuberant market" with buyers from around the world.

"Participation in our major sales is more global than ever, with buyers from growing markets in South America, Asia, and the Middle East," she explained.

Monet's "Nympheas", one of the artist's water lilies works which Christie's estimates could sell for as much as $50 million, is among the highlights of the sales.

RICHEST BUYERS WORLDWIDE

Porter said the painting should provide a good test of the market's top echelons. He described it as a "classic, great important picture of the most desirable size, which should appeal to the richest buyers worldwide."

Wassily Kandinsky's "Studie fur Improvisation 8," which has a pre-sale estimate of $20 million to $30 million, is poised to set an auction record for the artist.

Sotheby's sale will feature nine works by Picasso, led by "Nature morte aux tulipes," which carries a $35 million to $50 million estimate, and "Femme a la Fenetre," which could fetch up to $20 million. Both are portraits of Picasso's lover and muse, Marie-Therese Walter.

Both auction houses will also offer contemporary and post-war art, which has often been eclipsed by Impressionist works.

Among Sotheby's' top lots is Rothko's "No. 1 (Royal Red and Blue)" from 1954, which could fetch as much as $50 million. Previous works by the artist set record prices of $72.8 million and $87 million.

Jackson Pollock's "Number 4" from 1951 is estimated to sell for $25 million to $30 million, while one of Francis Bacon's seminal screaming Pope paintings, not seen in public for decades, is set to fetch up to $25 million.

The Pollock is one of eight Abstract Expressionist works from a single collection, which is expected to bring in more than $100 million. Another half dozen offerings are each poised to sell for $10 million to more than $20 million at a sale that Sotheby's expects will bring in more than $300 million.

At Christie's a dozen works among the 74 on offer carry estimates of about $10 million to more than $30 million each, led by Andy Warhol's "Statue of Liberty," a 3D work expected to sell for more than $35 million.

Other top lots include Jean-Michel Basquiat's untitled work from 1981, which could fetch about $20 million and would set a record, and an untitled Franz Kline painting from 1962, which is estimated to bring in as much as $30 million.

Christie's also expects strong interest in the collection of television producer Douglas Kramer, which features a wealth of sought-after contemporary works.

The auctions kick off on Wednesday with Christie's sale of Impressionist and modern art, expected to take in $250 million. Sotheby's Impressionist and modern sale on Thursday, postponed by three days in the wake of superstorm Sandy, will be followed by both houses' Post-war and contemporary sales next week.

The Mei Moses Art Index, which tracks publicly sold art, said in its latest report that there is no consistent return advantage to buying high priced art over more modestly priced art.

It found the October sales in London showed an 8.5 percent compound annual return over the period when particular works were sold. An investment in the S&P 500 over the same period would have earned 5.6 percent.

"That was an extraordinary validation," Sotheby's president and CEO Bill Ruprecht said of the sales. "There's no question that there's been a terrific reception for the best works."

(Editing by Patricia Reaney and Andrew Hay)