An Andy Warhol portrait of Marilyn Monroe worth an estimated $200 million headlines this month's spring sales in New York that collectors say are among the most anticipated ever

Christie's expects Warhol's 1964 "Shot Sage Blue Marilyn" to become the priciest 20th century artwork when the auction house puts it under the hammer on Monday.

Not to be outdone, competitor Sotheby's is offering $1 billion of modern and contemporary art including the second helping of the famed Macklowe Collection, during its marquee week in May.

"The excitement is certainly unprecedented," Joan Robledo-Palop, a collector and CEO of Zeit Contemporary Art in New York City, told AFP, about the buzz surrounding this season's auctions.

The 40 inch (100 centimeter) by 40 inch silk-screen Warhol is part of a series of portraits the pop artist made of Monroe following her death from a drug overdose in August 1962.

They became known as the "Shot" series after a visitor to Warhol's "Factory" studio in Manhattan fired a gun at them, piercing the portraits which were later repaired.

Alex Rotter, head of 20th and 21st century art at Christie's, has called the portrait "the most significant 20th century painting to come to auction in a generation."

The current most expensive 20th century auctioned work is Picasso's "Women of Algiers," which fetched $179.4 million in 2015.

The auction record for a Warhol is the $104.5 million paid for "Silver Car Crash (Double Disaster)" in 2013.

Other highlights offered by Christie's include Jean-Michel Basquiat's "Portrait of the Artist as a Young Derelict" (1982), expected to go for more than $30 million, and "Untitled (Shades of Red)" by Mark Rothko, tipped to fetch up to $80 million.

The auction house is also offering three Claude Monet oil on canvases that are predicted to sell for upwards of $30 million each.