Works by Andy Warhol, the American pop artist, are the subject of what could be one of the art market’s biggest private deals.

The New York-based collectors Jose Mugrabi and his son Alberto are in talks to sell a substantial part of their collection of about 600 Warhols.

Sources close to the talks said the Mugrabis have been approached by a buyer from the Middle East who plans to display the collection at a dedicated Warhol museum in the Gulf.

It is not clear which works are under discussion but the extensive collection includes Twenty Marilyns, the celebrated silkscreen portrait of Marilyn Monroe created in 1962. The Mugrabis bought it at Sotheby’s in New York in November 1988, a year after Warhol’s death, for $3.96m, setting a new world record for his work.

This weekend Alberto Mugrabi would say only: “I can’t talk about it.” When asked about rumours of a sale of 50 works for £500m he said: “That’s too many pictures.”

The Gulf states are showing a surge of interest in western art. Abu Dhabi has signed a deal to create an offshoot of the Louvre and a new Guggenheim museum will be built on an adjoining site. There is speculation that a Warhol museum could be built nearby.

John Martin, the London-based co-founder of the Gulf Art Fair, said: “In terms of attracting visitors, Warhol is the obvious choice. As a modern brand name, no one is bigger than Warhol.”

Among the Warhol works owned by the Mugrabis are silkscreens of Chairman Mao — in fuchsia pink — Elizabeth Taylor, John Lennon, Jacqueline Kennedy, Mick Jagger, Debbie Harry, Sylvester Stallone and Michael Jackson. The family began collecting in earnest in the early 1990s and appear to have timed the impending sale to perfection.

Last autumn, Artprice.com, an art market data service, calculated that Warhol’s paintings had more than quadrupled in value over the past decade, with a 30% jump in the first nine months of 2006.

In 2006 Alberto Mugrabi bid unsuccessfully at Sotheby’s in New York for a Warhol self-portrait painted in 1964. He explained: “I’m only helping my collection. If I don’t get it, I’m keeping the market healthy.”

Thomas Danziger, a New York lawyer who says he has acted for the family, said: “Jose Mugrabi saw, before other people, not only Warhol’s importance as an artist, but the economic upside of collecting him.”

Last month Alberto Mugrabi described Warhol as a blue chip investment equivalent to owning shares in Microsoft. This week a 1963 Warhol silkscreen, Green Car Crash, will be auctioned at Christie’s in New York. The estimate is £17.5m.

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