By David Willey BBC News, Milan

Maria Callas became one of the world's most celebrated sopranos

Bidding is expected to be brisk when a collection of memorabilia belonging to the late opera diva Maria Callas goes under the hammer at Sotheby's in Milan on Wednesday.

It will also be bitterly contested - both private collectors and the Greek government are vying to get their hands on the 330 lots, which include love letters, dresses, wigs and private gifts.

A museum devoted to Callas' memory in Athens has so far accumulated only a small number of personal items.

As a result, the Greek government has allocated a special fund to bid at the Milan auction.

Their representative was consistently outbid at the last auction of Callas souvenirs in Paris seven years ago, and the museum secured little more than a wig and a pair of gloves that once belonged to her.

Callas died a recluse at the age of 53 in Paris 30 years ago. She left $14m (£6.8m) and no will.

Love letters to husband Giovanni Battista Meneghini will be sold

Many of her personal effects were purchased at auction in the French capital the year after her death by her grief-stricken wealthy Italian industrialist husband Giovanni Mattista Meneghini.

He was 28 years her senior, and never got over the fact that she left him after being seduced by the wealthy Greek ship-owner Aristotle Onassis.

Meneghini and Callas were an odd couple in many ways. He had been a brick manufacturer with few cultural interests apart from a passion for opera, but he became her devoted manager and the couple were inseparable for a decade until she suddenly dumped him in 1959.

He then became a semi-recluse, suffering from heart trouble, and died in 1981.

His estate has now instructed Sotheby's to sell his large collection of personal memorabilia belonging to the great diva.

It had remained untouched for three decades, gathering cobwebs in a Paris attic and in his house on Lake Garda in Italy, until his heirs decided to sell.

The auction includes several evening dresses worn by the star

The collection includes furniture, musical scores, china, designer dresses, paintings and gifts from Callas' admirers around the world.

One item is a silver Tiffany bowl engraved with the words: "To Maria Callas who fulfils the prophecy of President Kennedy. Our Generation shall be remembered for its artists."

The dresses include a jade green chiffon evening gown by her Milanese fashion designer friend Elvira Leonardi Bouyeure - known better as Biki - which Callas wore at one of her last public performances in Carnegie Hall in New York in 1974.

But it is the 63 love letters from Callas to Meneghini "to be sold as a single lot" that are expected to attract the biggest interest and the highest price in the auction.

The reserve price is $72,000 (£36,000), but they could easily fetch $500,000 (£245,000) - perhaps more.

Written between 1947 and 1950, they show Callas' deep affection for Meneghini.

On the day she sang Norma in Buenos Aires in 1949, the role for which she is perhaps best remembered, Callas wrote: "I am writing on the day of the crucial test, the day of the great 'bel canto' lesson I will give to everyone all over the world."

Another letter is inscribed: "I want the best in everything but my art comes first."

Underwear

In the early days of their relationship, Callas sometimes wrote to Meneghini two or three times a day. He kept all her letters.

Under his tutelage, Callas was transformed from the "fat, awkward girl" described by one biographer into an elegant, sophisticated international jet-setter.

There have been several other auctions of Maria Callas' personal possessions, such as the sale of her jewellery in Geneva in 2004.

The most notorious was a much-criticised sale of intimate items, including her underwear, in Paris in 2000.

Bidding for Callas' sheer black hose exceeded $3,000 (£1,470).

Three decades after her death, the memory of Maria Callas still exercises a powerful hold over the public in Milan, where she scored many of her greatest triumphs at La Scala opera house.

Yet another exhibition - called Fashion and Myth - has just opened here, sponsored by the city hall.