"In the course of the coming days, Iran will implement and announce the suspension of uranium enrichment," Hamid Reza Asefi told reporters, without giving further details.
The IAEA in September asked Iran to do three main things ahead of a November 20 board meeting: fully disclose its nuclear programme, agree to tougher inspections and suspend the enrichment of uranium that could be used to make an atomic bomb.
Iran has already made what it says is a full declaration of its nuclear programme, and says it will next week also send a letter to the Vienna-based watchdog stating its intention to sign an additional protocol to the Non-Proliferation Treaty (NPT) that would subject it to a vigorous inspections regime.
Iran agreed to comply with the demands on October 21, when the British, French and German foreign ministers visited Tehran to seek a way out of the dispute over the country's bid to generate nuclear power -- seen by the US as a cover for secret weapons development.
A suspension of enrichment activities is seen as crucial by the IAEA as it tries to fully uncover the Islamic republic's nuclear programme.
The problem centres on traces of highly enriched uranium which IAEA inspectors found at two sites in Iran during previous visits.
The Iranians say the particles came from contamination from equipment they bought aboard, but the IAEA wants enrichment inside Iran to be halted while it verifies the equipment, and also pending Iran's submission to the tougher safeguards enshrined by the additional protocol.
Although Iran is expected to declare its readiness to sign the text, the country's top national security official said Sunday that IAEA inspectors will not be granted access to sites in Iran that are not related to its nuclear programme.
"Next week the Islamic Republic of Iran will give a letter on the additional protocol," Hassan Rowhani, who as secretary of Iran's Supreme National Security Council is charged with the nuclear dossier, told state television.
"In this letter we will state that the IAEA will not be permitted to enter sites that are not linked to Iran's nuclear activities."
Although Rowhani appeared to be attaching conditions to the application of the additional protocol, a diplomat close to the discussions emphasised there was no need for immdiate alarm that Iran was making some kind of U-turn.
"Iran can express reservations, but the text of the additional protocol is standard," said the diplomat, who asked not to be named.
The source explained that once Iran signed the text, it would only be subject to unlimited inspections of declared facilities related to its nuclear activities.
As for suspect sites, he pointed out that the IAEA would have to respect a specific procedure for securing visits.
Iran raised concerns over visits to military and holy sites in the Islamic republic, citing national security and sovereignty concerns, when the three European ministers visited.
"It's not going to be like Iraq, with UNSCOM (arms inspectors) kicking down doors and this kind of thing," said the diplomat.
"And Iran is entitled to remind the IAEA of this when it sends the letter. But there is no question of a special text just for Iran."