The head of the U.N. nuclear agency is sounding a note of caution about Iran’s claims that it is not interested in nuclear arms, saying he cannot guarantee that all the country’s atomic activities are civilian in nature.

Though not new, Yukiya Amano’s comments Monday are significant amid a renewed deadlock in the 12-year probe by his International Atomic Agency of suspected nuclear weapons work by Iran.

Iran denies such activities.

Amano’s comments also come as the U.S. and five other powers try to persuade Tehran to allow the IAEA greater sleuthing powers, allowing the agency to do snap inspections of sites suspected of possible unreported nuclear work.

Amano told an IAEA meeting in Vienna that his agency cannot “conclude that all nuclear material in Iran is in peaceful activities.”

(AP)