The head of the U.N. nuclear agency says he is hopeful that Iran will stay faithful to its pledge to stop building nuclear centrifuges.

One day after nuclear inspectors arrived in Iran to verify that the country has stopped all uranium enrichment activities, the chief of the International Atomic Energy Agency (IAEA), Mohammed ElBaradei, said he hopes Iran will speed up its cooperation with the international nuclear watchdog group.

"Things were slow for awhile," he said. "I had to go to Iran a couple of weeks ago. I told them they needed to accelerate cooperation, and I got the satisfactory plan of action and I hope that will be implemented in the next couple of months."

Speaking to a group of faculty and students at Cairo University, Mr. ElBaradei said Iran had kept hidden its nuclear program for 18 years, and though he doesn't have proof that Iran is producing nuclear weapons now, greater transparency on Iran's part will only help finish the process.

Iran opened its nuclear program to international inspectors last year, but concealed some elements that the IAEA later uncovered. Iran has repeatedly said its nuclear activities are for peaceful purposes. The United States believes Iran is hiding plans to build nuclear weapons.

The U.N. nuclear chief also said his agency has asked to continue nuclear inspections in Iraq for three more months, and is waiting for approval from the U.N. secretary general.