Tehran cuts ties with British Museum over Persian treasure

Iran has cut all its ties with the British Museum over its decision to delay the loan of a 2,500-year-old Persian treasure, the Cyrus Cylinder, in the latest sign of worsening relations between Tehran and London.

The clay tablet is believed to be the world's first declaration of rights and the British Museum says it needs to keep it until the summer as experts have made a ground-breaking discovery that could lead to the decoding of missing text.

But Iran's state-run Cultural Heritage Organisation said the museum's decision was politically motivated. "[We have] cut all relations and co-operation with the British Museum," said the group's head, Hamid Baghaie, adding that Iran would incur considerable costs because of the delay. He said Iran would file a complaint to Unesco, the UN's cultural agency, because the British Museum had missed yesterday's deadline to hand back the cylinder.

A spokeswoman for the British Museum said the move was "a big surprise". "The British Museum has acted throughout in good faith, and values highly its hitherto good relations with Iran," she added.

The museum had promised to lend the Persian treasure to Iran for two months starting in January. But it delayed the loan until the summer so its experts could continue research on the cylinder, which is linked to Cyrus the Great's conquest of Babylon. He is regarded as one of ancient Persia's greatest historical figures. He captured Babylon, in modern Iraq, and freed Jews held captive there.

The row threatens to further deepen tensions between Britain and Iran, which are already at loggerheads over the Islamic Republic's nuclear-energy programme and the disputed presidential election last June.