TEHRAN — The final step for Iran to start carrying out the nuclear agreement was completed Wednesday, after an oversight panel ratified the bill passed by Parliament supporting the deal with six world powers.

The ratification by the veto-wielding panel, the 12-member Guardian Council, made within 36 hours after Parliament accepted the details of the agreement, now clears the way for the Atomic Energy Organization of Iran to start dismantling thousands of centrifuges and redesign a heavy-water reactor into a much less a dangerous light-water reactor. It also needs to take several other measures.

In exchange, as soon as the International Atomic Energy Agency verifies the steps, sanctions against Iran will be lifted.