From left to right: European Union High Representative Federica Mogherini, Iranian Foreign Minister Mohammad Javad Zarif, Head of the Iranian Atomic Energy Organization Ali Akbar Salehi, Russian Foreign Minister Sergey Lavrov, British Foreign Secretary Philip Hammond and US Secretary of State John Kerry pose for a group picture at the United Nations building in Vienna, Austria, Tuesday, July 14, 2015. After 18 days of intense and often fractious negotiation, diplomats Tuesday declared that world powers and Iran had struck a landmark deal to curb Iran's nuclear program in exchange for billions of dollars in relief from international sanctions, an agreement designed to avert the threat of a nuclear-armed Iran and another U.S. military intervention in the Muslim world. (Joe Klamar/Pool Photo via AP)

From left to right: EU High Representative Federica Mogherini, Iranian Foreign Minister Mohammad Javad Zarif, Head of the Iranian Atomic Energy Organization Ali Akbar Salehi, Russian Foreign Minister Sergey Lavrov, British Foreign Secretary Philip Hammond and US Secretary of State John Kerry, all pose for a group picture at the United Nations building in Vienna, Austria, Tuesday, July 14, 2015. (Joe Klamar/Pool Photo via AP)

A UN atomic agency has said it believes that Iran worked in the past on nuclear weapons but its activities did not go past planning and basic component experiments.

The assessment was contained in an International Atomic Energy Agency (IAEA) report, ending nearly a decade of attempts to investigate the allegations.

The evaluation said the most “coordinated” work on developing such arms was done before 2003, with some activities continuing up to 2009.

The agency’s probe was based on intelligence provided by the United States, Israel and other Iranian adversaries and on the IAEA’s own research and interviews.

The confidential report released by the IAEA on Wednesday and obtained by reporters is significant in wrapping up the probe and in preparing the ground for the lifting of sanctions on Tehran.