The UN has urged Iran to show it is taking action to preserve a historic city square threatened by the building of an office block nearby.
Unesco says building work near Isfahan's square has halted
Isfahan, famed for the minarets and domes of its Naqsh-e Jahan square, was put on the World Heritage List in 1979.
Unesco, the UN's cultural body, says Iran must reduce the height of the new tower or ruin views of the square.
Iran has until 1 February to submit a report showing its progress in complying, to be considered in July.
Unesco warned at its annual conference last June, held in the ancient Chinese city of Suzhou, that the city of Isfahan could be in danger because of "uncontrolled urbanisation".
Officials will decide this summer, having studied Iran's report, whether to consider moving Isfahan on to its World Heritage in Danger List.
Naqsh-e Jahan square, built at the beginning of the 17th Century, is twice the size of Moscow's Red Square and the focal point of Isfahan.
Junko Taniguchi, a Unesco official in Tehran, said construction of the Jahan Nama shopping and office complex did appear to have halted.
She told the BBC News website she was confident Iran would stick to plans to reduce the height of the tower.
"We have not discussed putting it on the World Heritage in Danger List," she said. "That process is a very serious step for any government or Unesco."
Other countries where heritage sites were considered to be at risk had also been asked to submit a report in February, she added.