Ban issued a statement to a disarmament and non-proliferation conference at the Monterey Institute of International Studies in California. He said that while the Nuclear Non-Proliferation Treaty has shown its effectiveness, his sentiment on overall disarmament programs was "mixed."
"I am deeply concerned about Iran's nuclear program," he stressed.
U.N. nuclear inspectors ended two days of meetings last week in Iran without gaining access to the controversial Parchin military complex. Iran is suspected of having a military dimension to its nuclear program, an allegation the government denies.
He added that a North Korean decision in December to deploy a long-range rocket renewed concerns about Pyongyang's ambitions.
"Countries in Northeast Asia are in transition, which can offer a new window of opportunity for the Democratic People's Republic of Korea," Ban said. "I encourage the new leadership in Pyongyang to build confidence with neighboring countries and address the concerns of the international community."
North Korean rocket launches in 2006 and 2009 coincided with the country's first two nuclear tests.