The head of the International Atomic Energy Agency says Iran will allow inspectors to visit its newly revealed uranium-enrichment site on October 25.
Mohamed ElBaradei says inspectors need access to the site to ensure it is for peaceful purposes, as Iran maintains.
The IAEA director spoke in Tehran, following talks Iranian officials say were unconnected to the Qom facility.
While ElBaradei has said Iran was "on the wrong side of the law" in not disclosing the plant's existence earlier, he used the news conference to sound a note of caution about Iran's intentions.
"The agency has no concrete proof that there is an ongoing weapon program in Iran," ElBaradei said. "There are allegations that Iran has conducted weaponization studies, however this is an issue we are still looking into in."
The New York Times reported Saturday the IAEA has tentatively concluded Iran has the know-how to design and build a nuclear weapon.
That report, plus the revelation last month of the nuclear plant near Qom, has sharpened international focus on the Iranian program.
Even with the new concerns, ElBaradei, whose soon-to-end tenure at the IAEA has been marked by moderation, welcomed the changed tenor of dialogue between the international community and Iran.
"I have been saying for a number of years that we need transparency on the part of Iran; we need cooperation on the part of the international community," ElBaradei said. "So, I see we are at a critical moment. I see we are shifting gears from confrontation into transparency and cooperation."
Negotiations between Iran and other nations have picked up recently, with talks last week in Geneva, and more, announced Sunday, set for October 19 in Vienna.
Officials say the Vienna talks will focus on possibly sending Iran's uranium overseas for enrichment. Third party processing could ensure the material is enriched only to the point needed for civilian purposes, and below the level called for in nuclear weapons.