Iran may say repeatedly that its nuclear program is strictly peaceful, but the country is not allowing the world's top nuclear watchdog to confirm that assertion.

"We still cannot give the assurance that all of the activities in Iran are for peaceful purposes," International Atomic Energy Agency (IAEA) Director General Yukiya Amano told CNN this week.

"We have two problems: one is that Iran is not fully cooperating with the Agency to clarify the information that may have military aspects," Amano continued. "Another problem is that Iran is not allowing us to implement a more powerful verification tool which is called an 'Additional Protocol.'"

A de-classified 2007 National Intelligence Estimate concluded that Iran suspended its race for a bomb in late 2003. However, it also noted that smaller-scale activity continued and warned that “Iran probably would use covert facilities — rather than its declared nuclear sites — for the production of highly enriched uranium for a weapon.”

Iran denies claims that it ever had a weapons program and says any documents suggesting it did are fabricated. But there's no way for the IAEA to know for sure if Iran keeps stonewalling the agency.

"We ask Iran to fully cooperate with us so that we can provide the assurance that all the activities in Iran is in peaceful purpose," Amano said repeatedly on CNN.

The New York Times refers to Iran's potential nuclear weapons capability as "a delicate question that has been little discussed in public: how to design an agreement to maximize the chances that Western intelligence agencies would catch any effort to develop an atomic bomb at a covert site."

The current deal focuses on how to deal with Iran’s three major “declared” nuclear facilities so that there is sufficient time to notice if Iran attempts to produce enough fuel for a bomb. But the risk of a bomb being built in secret is greater.

"Unstated is the fear of a more problematic issue, referred to as 'sneakout,'" The Times notes. "That describes the risk of a bomb being produced at an undetected facility deep in the Iranian mountains, or built from fuel and components obtained from one of the few trading partners happy to do business with Tehran, like North Korea."