Iranian technicians, work with foreign colleagues at the Bushehr Nuclear Power Plant, just outside the southern port city of Bushehr.

Iran did work related to developing nuclear arms in the past, the U.N. atomic agency concluded in a report that wraps up a near decade of investigations and opens the way to implementing a landmark deal aimed at reducing any future nuclear threat from Tehran.

Iran has consistently denied any interest in nuclear arms or past work on such weapons, and Iranian Deputy Foreign Minister Abbas Araqhchi told Iranian television that the International Atomic Energy Agency report “confirms the peaceful nature” Iran’s nuclear program.

But the report contested that view and came down on the side of U.S. allegations, saying the agency “assesses that a range of activities relevant to the development of a nuclear explosive device were conducted in Iran prior to the end of 2003 as a coordinated effort, and some activities took place” up to 2009.

At the same time, the report said any such work was restricted to “feasibility and scientific studies” that stopped short of the advanced development of such weapons.

No previous IAEA report has so clearly linked Iran’s past nuclear work to weapons development.

At the same time, the agency described its finding as an assessment and left a final ruling on whether the case should be closed in the hands of Washington and other leading nations represented on the IAEA’s 35-nation board.

That decision is tentatively set for Dec. 15, when the board meets to decide whether to endorse the deal. Expected approval would close the IAEA investigation and fulfill a key requirement of the July 14 nuclear deal between Iran and six world powers.

That deal specifies that the agency must be in the position to wrap up the probe and deliver its views as a key condition for the start of an end to nuclear-related sanctions on Tehran. In exchange, Tehran must cut nuclear technologies that could be used in the future to build a bomb.

Beyond its drive for an end to all sanctions imposed on it over its atomic activities, Iran attaches huge importance to closing the books on the allegations in its drive to lift all punitive measures against it and wipe the slate clean over its nuclear program.

Israel, Iran’s implacable foe, urged further pressure on Tehran. Prime Minister Benjamin Netanyahu asked the IAEA to “continue to deepen the investigation,” saying Iran’s past was relevant to the “current status” of its nuclear program.

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