Iran should simply renounce the NPT and withdraw, telling the IAEA to go fly a kite. It has been done be others, most notably Israel. There is no reward to signing the NPT and no penalty for refusing to do so. This makes the NPT and the IAEA useless.
22 Emirati troops from Saudi-led coalition killed in Yemen (AP)
from the article: IAEA chief to Iran: Stop obstructing nuclear investigation