Iran has resolved questions posed by the UN's nuclear watchdog about its plutonium experiments, Tehran says.
UN inspectors can visit the Arak plant under the agreement
The claim was made in a text outlining a timetable for co-operation with the International Atomic Energy Agency, which was agreed at talks last week.
It would be the first serious issue closed by the IAEA during its four-year inquiry into Iran's nuclear activities.
Western powers suspect Iran of building a nuclear weapons capability. Tehran says its nuclear programme is peaceful.
The UN Security Council has already imposed two rounds of sanctions against Iran for defying its calls to halt uranium enrichment and plutonium reprocessing, and answer IAEA questions.
The five-page text of the Iran-IAEA accord was released in Vienna on Monday.
It said the IAEA accepted that "earlier statements made by Iran [on the issue of plutonium] are consistent with the agency's findings, and thus this matter is resolved."
Iran also said it would co-operate on resolving concerns over documents that allegedly show Iran has a secret military project for developing nuclear arms.
However, it dismissed the claims as "politically motivated" and "baseless allegations".
Last week, Iran and the IAEA announced that they had agreed a timeline for implementing a plan to clarify Tehran's nuclear programme, first announced in July.
However, US envoy to the IAEA, Gregory Schulte, said the plan had "real limitations" and accused Iran of manipulating the IAEA as a way to avoid harsher sanctions.
He said Iran was still defying the UN's key demand for it to halt its uranium enrichment activities and said the US would continue to push for a third round of sanctions.