Iran had said on July 13 that it would let IAEA inspectors visit the reactor, which is under construction and is due to be completed in 2009.
The UN has previously imposed sanctions over Iran's nuclear programme and has warned of more punitive action.
The US fears the Arak reactor could provide plutonium for weapons, while Tehran insists its programme is for civilian use.
The IAEA has blocked technical co-operation for the reactor.
Iran's ambassador to the IAEA, Ali Asghar Soltanieh, has said that "just one visit (to Arak) will be enough" for the inspectors.
Iran has other sites that convert and enrich uranium to produce nuclear fuel, a process the West says could be diverted to an alleged weapons programme.
Mohammad Ali Hosseini, Iran's foreign ministry spokesman, confirmed another team of IAEA experts would visit the country on August 6 to discuss inspections of the Natanz facility.
Iran will then hold a third round of talks with IAEA officials in Tehran on August 20, he said.
The UN Security Council has repeatedly called on Iran to freeze its uranium enrichment and halt construction of the Arak reactor.