Speaking at Hankuk University, mostly to students, Obama also pledged to work with Russia and China. He spoke ahead of the 2012 Seoul Nuclear Security Summit in Seoul aimed at reducing the nuclear terrorism threat.

The two-day summit in the South Korean capital will focus on international measures to protect nuclear materials and facilities from terrorism threats. The heads of 40 countries are expected to attend.

Obama said "serious sustained global effort" was needed to protect the world from the nuclear terrorism risk.

Pyongyang has been subjected to several rounds of UN Security Council sanctions since it declared itself a nuclear power in 2005. The state broke off talks with South Korea, China, the United States, Japan and Russia on its nuclear program in April 2009, after the UN Security Council passed a resolution condemning its missile tests.

In February, North Korea agreed to suspend nuclear activities and allow inspectors from the International Atomic Energy Agency (IAEA) to monitor compliance.

In his speech, Obama addressed North Korea's nuclear ambitions, saying that his country has ''no hostile intent'' towards Pyongyang, but added that ''there will be no rewards for provocation.” He said North Korea had better give up its plans to launch a long-range missile to put a satellite in orbit.

''You can continue with the road you are on but we know where that leads,'' he said addressing the North Korean leadership as quoted by the BBC.

Regarding Iran, Obama said the problem over its nuclear program can still ber resolved through diplomatic means but warned the Islamic Republic that “time is short.”

''Iran must act with the seriousness and sense of urgency that this moment demands,” he said.

Western countries led by the United States suspect Iran of seeking to build nuclear weapons, but the Islamic Republic insists it needs nuclear power solely for civilian purposes.