A letter that could fuel the long-running international dispute over the ownership of the Elgin Marbles is to be sold at auction for an estimated �1,000.

The handwritten note will be sold at Dominic Winter Auctions in Wiltshire on 6 November and is thought likely to spark interest among both sides in the argument between the UK and Greek authorities.

The letter was written in 1811 by the British Ambassador to Constantinople (Istanbul), Robert Adair, and addressed to Thomas Bruce, the seventh Earl of Elgin.

It suggested the earl had no right to buy the 5th Century marbles.

The sculptures, which originally adorned the front of the Parthenon temple in Athens were taken by the earl to England in 1811, and are now housed at London's British Museum.

Greece wants them returned for the 2004 Olympics

Dominic Winter's valuer Chris Albury said the letter was a significant find but that its contents could be open to historical interpretation.

"What is clear is the content of the letter fuels the campaign for the restitution of the Marbles from the British Museum to Athens. <

"As far as we have been able to ascertain it is a unique document. It is likely to be seized upon by both sides of the argument," he said.

The marbles date from between 447 and 432 BC and depict the most formal religious ceremonies of ancient Athens - the Panathenaea procession.

The Earl of Elgin was given permission to work on the marbles' protection in 1801.

Greece was still under Ottoman (Turkish) control and the sculptures' fate was considered in jeopardy.

Pollution

The UK and Greek authorities have been arguing over whether the marbles should be returned to Greece since then.

The campaign Parthenon 2004, backed by more than 90 UK MPs and public figures, is calling for the marbles to be returned to Athens in time for the next Olympic Games.

The Greek authorities are building a specially designed display "case" for the marbles on top of a �29m museum to show the frieze in its original situation.

And those calling for their return to Athens have included high-profile figures.

Lord Byron wrote a poem, The Curse of Minerva attacking Elgin's "looting" of the marbles and more recently Hillary Clinton has been asked for their return.

Supporters of the lobby to keep the marbles in the UK say housing them in the British Museum has saved them from deterioration caused by pollution in Greece.