A few hours ago, the International Atomic Energy Agency announced a “milestone” agreement with Iran. According to IAEA spokeswoman Melissa Fleming, the U.N. nuclear watchdog and Tehran will cooperate “on a process that aims to clarify the so-called alleged studies during the month of May.” The “alleged studies” are materials supplied by the United States and other Western nations showing that Iran had at one time conducted nuclear bomb research.

Iranian officials and the IAEA’s chief investigator, Olli Heinonen, negotiated the agreement during talks on Monday and Tuesday in the Iranian capital. Previously, Mohamed ElBaradei, the organization’s chief, had said that the world “needs to make sure Iran did not have a weapons program.”

For Tehran, the agreement with the IAEA is obviously another delaying tactic. Yet the deal also creates a deadline. If the Iranians cannot refute the alleged studies by next month and cannot admit that they had tried to weaponize the atom, then the international community faces another one of those moments of truth.

Deadlines do not enforce themselves. Great powers do that. By the end of next month we will know whether the United States is still a great power. Iran is not just about the Middle East, and it is not just about Syria and all the other nations that want the bomb. Iran is now about us.