SEOUL, Republic of Korea - President Obama paused during his speech to local college students in South Korea Monday to directly address the North Korean leaders across the DMZ, urging new dictator Kim Jong-un and his regime to pursue a different path.

Saying he wanted to "speak directly to the leadership in Pyongyang," the president insisted that the United States was "committed to peace" and has "no hostile intent toward your country." That said, Mr. Obama scolded North Korea, saying its "provocations and pursuit of nuclear weapons have not achieved the security you seek, they have undermined it. Instead of the dignity you desire, you are more isolated. Instead of earning the respect of the world, you have been met with strong sanctions."

Mr. Obama urged the North Koreans to change their ways. "Today we say, Pyongyang: have the courage to pursue peace and give a better life to the North Korean people," he said.

The president also addressed Iran's pursuit of nuclear weapons, saying, "There is time to solve this diplomatically, but time is short."

The speech, at Hankuk University of Foreign Studies, focused on the Nuclear Security Summit that kicks of later today, with the president heralding progress made in securing the world's vulnerable nuclear materials.

While repeating his lofty goal for a world without nuclear weapons, the president said he would continue to "maintain a safe, secure and effective arsenal that guarantees the defense of the United States and our allies-including South Korea and Japan."

That said, the president argued that with more than 1,500 deployed nuclear weapons and more than 5,000 warheads, the U.S. has "more nuclear weapons than we need."

The president said in May he would work with Russian President Vladimir Putin on reducing both countries' stockpiles of nuclear warheads, "but also tactical weapons and warheads in reserve." He also said his administration continue to pursue ratification of the Comprehensive Test Ban Treaty. And, given the need for forms of energy that are alternatives to fossil fuels, the president heralded "the astonishing benefits that nuclear technology has brought to our lives."

The president announced a new agreement with several European nations that will preserve the use of medical isotopes to treat cancer and heart disease without using highly enriched uranium.

-Jake Tapper