Post-war art takes center stage in the upcoming spring art auctions in New York and with the market booming, new records are expected to be set for several painters including Mark Rothko. Auctions of Impressionist and Modern art, normally the biggest draw of the art season, begin next week at Sotheby's and Christie's. But at Contemporary art sales at the archrivals the following week, works by Rothko, Francis Bacon and Jackson Pollock are all poised to break the 27.1 million U.S. dollars post-war record set by a de Kooning last autumn. While prices for top later-20th century works have nipped at the heels of the traditionally dominant Impressionist and Modern works for years, they have rarely topped U.S. $20 million. This year at the Sotheby's Contemporary auction, Mark Rothko's "White Center (Yellow, Pink and Lavender on Rose)" is expected to top 40 million USD and Francis Bacon's "Study From Innocent X" is seen fetching in excess of 30 million dollars. While these high hammer prices are expected at the Contemporary sale, the highest estimated work at Sotheby's Impressionist and Modern sale is in the region of 20 million USD. Auction house officials at both Sotheby's and Christie's say several factors are driving prices at the upper echelons of the market for newer works. "There is certainly a scarcity in my colleague's field, Impressionists and Modern, with really truly extraordinary examples of 20th century art , although they have several in this sale as well and so collectors have moved over a little bit into this collecting field. So someone who might buy an extraordinary, late Picasso is going to be interested in Liechtenstein, or is going to be interested in Rauschenberg or is going to be interested in Rothko," explained Anthony Grant, Sotheby's senior specialist for Contemporary art. Supply is another factor, with the most desirable Impressionist and Modern works already hanging in museums. By contrast, many of the more sought-after Warhols and Rothkos have been in private hands for 25 years or more and are now moving into the open market. Said David Norman, Sotheby's Chairman of Impressionist and Modern Art, "What we also see is, as the available supply of great pieces diminishes, people start looking for where they find the same quality and style of works in other categories. So if the French artist at the turn of the century like Matisse uses strong colour, are unavailable or if they are they're tens of millions, we've seen a shift of interest to the German Expressionists, artists who use the same strength of colour within a few years of the French, and that market is starting to rise." This can be seen in the presence of works by Lyonel Feininger and Paul Klee. Rothko's "White Center (Yellow, Pink and Lavender on Rose)" from 1950 is being auctioned for the first time. The Abstract Expressionist work being sold by Sotheby's on behalf of philanthropist David Rockefeller is the most expensive work hitting the block during two weeks of sales -- the first time a Contemporary painting rather than an Impressionist work is billed to sell for the top amount. Also at Sotheby's is Bacon's "Study From Pope Innocent X," estimated in excess of U.S. 30 million USD. Pollock's "Number 16, 1949" and de Kooning's "Untitled I" could surpass the 25 million range. Both Sotheby's and Christie's hope to take in close to the half a billion dollars between the two houses from Contemporary sales. Auction executives say their high estimates reflect steep prices commanded in private sales in recent years. Last year a private sale of a Pollock reportedly brought 140 million USD, making it the most expensive painting ever sold. Impressionist and Modern works continue to generate big numbers. Sotheby's is offering a Matisse painting estimated at 15 million U.S. dollars to 20 million and a Cézanne still life priced at 14 million USD to 18 million. Sotheby's sales kick off on May 08 with of Impressionist and Modern art, followed by the Contemporary auction on May 15.