Iran's deputy nuclear chief is denying a report that technicians have dismantled the core of the country's nearly finished heavy water reactor and filled it with concrete as part of Tehran's obligations under the nuclear deal with the West.

Ali Asghar Zarean, in remarks to state TV Tuesday, dismissed the report by the Fars news agency report from the previous day. He says Iran will sign an agreement with China to modify the Arak reactor, a deal that is expected next week.

Under the nuclear agreement, Iran must redesign the Arak reactor so it can't produce plutonium for nuclear weapons.

Zarean says once modifications are done and Arak goes online, Iran hopes to export excess heavy water produced there to the U.S. through a third country, for uses in research.