The cache of tablets including the treaty was unearthed last summer at the site of an ancient temple at Tell Tayinat, located in southeastern Turkey.

Known as the Vassal Treaties of Esarhaddon, the 43 by 28 centimetre tablet contains about 650 lines and is in a very fragile state.

"The tablet is quite spectacular," said Professor Timothy Harrison of the University of Toronto.

"It records a treaty -- or covenant -- between Esarhaddon, King of the Assyrian Empire and a secondary ruler who acknowledged Assyrian power."

"The treaty was confirmed in 672 BC at elaborate ceremonies held in the Assyrian royal city of Nimrud (ancient Kalhu)."

"In the text, the ruler vows to recognize the authority of Esarhaddon's successor, his son Ashurbanipal."

"The treaties were designed to secure Ashurbanipal's accession to the throne and avoid the political crisis that transpired at the start of his father's reign."

"Esarhaddon came to power when his brothers assassinated their father, Sennacherib."

The 7th century BC marked the rise of the Phrygians and other rival powers in highland Anatolia on the north-western frontier of the Assyrian empire.

This was also the time of the divided monarchy of Biblical Israel, as well as increased contact between the Levantine peoples of the Eastern Mediterranean and Egypt, as well as the Greeks.

It is hoped that analysis of the clay tablet will shed a light on the complexities of geopolitical relations in the ancient world.

"It will take months of further work before the document will be fully legible," said Professor Harrison.

"These tablets are like a very complex puzzle, involving hundreds of pieces, some missing."

"It is not just a matter of pulling the tablet out, sitting down and reading."

"We expect to learn much more as we restore and analyse the document."