The Greek government hopes the return of a heel will strengthen its hand
A German university has backed the return of a fragment of the Parthenon temple to Athens but it wants Greece to give it an artwork in return.
The piece of marble - a carving of a man's heel - from the frieze of the ancient temple measures 11cm by 8cm.
The Greek government has hailed the university of Heidelberg's decision as "a highly important symbolic gesture".
It hopes it will boost its case for the return of the Parthenon, or Elgin, marbles in the British Museum.
The heel is from one of the slabs of the frieze which ran round the top of the 2,400-year-old temple, depicting a religious procession in ancient Athens.
Most of the what survives of the slab is in the Acropolis Museum in the Greek capital.
The British Museum wants to keep its Parthenon marbles
The Greek government has for years campaigned for the return of the British Museum's Parthenon marbles - most of the surviving parts of the frieze and other sculptures.
These were removed by British envoy Lord Elgin at the beginning of the 19th Century.
The museum says it is not at liberty to return the sculptures, and believes they are well looked after and available for millions of visitors to see in London.
Heidelberg University vice-rector Angelos Chaniotis told the BBC News website that the return had been agreed "because the scientific, cultural, and educational significance of this fragment consists exclusively in it joining other fragments in Athens."
"The transfer would be in exchange for another work of art. The object of the exchange will be subject to negotiations between the university and the Greek ministry of culture," he went on.
It is not known how the fragment arrived at Heidelberg, where it was first recorded in 1871.
"It may be assumed that it was originally taken as a "souvenir" by a traveller in the 19th century and donated to the university," said Mr Chaniotis.