Germany's Tuebingen University and Italy's Udine University have led research into Qatna, a Bronze Age city that lasted for thousands of years. This season they had planned to dig into its founding layer, dating from about 3000 BC.

A Tuebingen spokesman said the dig was off because of the "unclear situation" in Syria.

Syria has been the scene of anti-government protests for months and a violent crackdown by security forces.

"A plan to put up an archaeologists' building has also been frozen," he said.

Qatna sat aside trade routes between Egypt and Mesopotamia and was the capital of an ancient kingdom.

The Italo-German dig aims to rediscover how it was built and how it looked. The evidence shows it was a laid-out town on a square pattern, occupying 100 hectares. Past digs have found cuneiform tablets and a royal burial chamber in the ruins of its palace.