Under the new plan, Tehran wouldn’t be expected to immediately clarify all the outstanding questions raised by the IAEA in a 2011 report on Iran’s alleged secretive work. A full reckoning of Iran’s past activities would be demanded in later years as part of a nuclear deal that is expected to last at least 15 years.

“PMD is important and has always been part of the package,” said a senior European official involved in the Lausanne talks.

White House spokesman Josh Earnest indicated Wednesday that a final agreement on Iran’s nuclear program would address the IAEA’s concerns.

“Those ongoing disagreements about Iran’s compliance with inspections related to the possible military dimensions of their program are something that we would expect to resolve in the context of these ongoing talks,” Mr. Earnest said.

Iran has denied it has pursued nuclear weapons and charges that the IAEA’s dossier is based on falsified documents provided by Israel and other Western countries.