VIENNA — Iranian scientists experimented with technologies that could be used to make a nuclear bomb without ever taking the final steps needed to turn their work into a weapon, international investigators said in a landmark report aimed at ending a 12-year inquiry.

International Atomic Energy Agency monitors concluded that Iran ceased work that could be used to develop a weapon by 2009, the Vienna-based agency found in a restricted report obtained Wednesday by Bloomberg News. Pending its approval by the IAEA’s board of governors at a Dec. 15 meeting, the document will close the weapons inquiry and bring Iran one step closer to relief from international economic sanctions.

“These activities did not advance beyond feasibility and scientific studies, and the acquisition of certain relevant technical competences and capabilities,” IAEA Director General Yukiya Amano wrote in the report. “The Agency has no credible indications of activities in Iran relevant to the development of a nuclear explosive device after 2009.”

IAEA inspectors will continue monitoring Iran’s nuclear work under special powers obtained through the Islamic Republic’s July accord with world powers, said two diplomats.

Iran has denied ever seeking a nuclear bomb and pledged to allow wider monitoring under the accord.