Vienna, Austria (CNN) — Iran is not open about its nuclear program, but it should be, the head of the U.N. nuclear watchdog agency said Wednesday.

“Iran is not telling us everything. That is my impression. We are asking Iran to engage with us proactively, and Iran has a case to answer,” said Yukiya Amano, the director general of the International Atomic Energy Agency.

Amano told CNN Senior International Correspondent Matthew Chance that Iran has declared a number of nuclear facilities to the IAEA, which has them under its safeguards.

“For these facilities and activities, I can tell that they are in peaceful purpose,” Amano said. “But there are also, there may be other facilities which are not declared, and we have the indication or information that Iran has engaged in activities relevant to the development of nuclear explosive devices.”

Also Wednesday, a Western diplomat here said that the five permanent members of the U.N. Security Council, plus Germany — the so-called P5 plus 1 — have agreed on a joint statement on Iran, which will be delivered Thursday to the IAEA.

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