U.S. President Barack Obama warned North Korea Monday about its pursuit of nuclear weapons, saying there would be no more rewards for provocations.

In a speech at Hankuk University in Seoul, South Korea, Mr. Obama said Pyongyang could continue down the road it is on, but that would lead to more broken dreams, more isolation and ever more distance between the people of North Korea and the dignity and opportunity they deserve.

The American president said the same applies to Iran. Mr. Obama told the audience that Iran stands alone, as the only member of the Nuclear Nonproliferation Treaty unable to convince the international community that its nuclear program is for peaceful purposes. He said the United States and other nations have offered to help Iran develop nuclear energy peacefully, but time and again Tehran has refused, taking instead what he called the path of denial, deceit and deception.

Mr. Obama said he will meet with the leaders of Russia and China Monday to discuss a diplomatic resolution to the situation, in which Iran fulfills its obligations.

Those meetings and others will take place on the sidelines of a two-day nuclear security summit in Seoul, focused on combating nuclear terrorism, but likely to be overshadowed by North Korea's plans to launch a satellite using a long-range rocket next month.

Leaders from more than 50 other nations and international organizations will gather in South Korea's capital for the second such nuclear meeting, which was first held in Washington in 2010.

Although not on the agenda, world leaders will likely turn their focus to North Korea's recent announcement that it will launch a satellite into space using a long-range rocket. The North says this is part of celebrations marking the 100th anniversary of the April 15 birth of its late founder and president Kim Il Sung.

The U.N., U.S., European Union, Russia and Japan have warned North Korea that its scheduled rocket launch is in violation of U.N. resolutions, and they have urged Pyongyang to abandon the plan. Even North Korea's ally China has expressed concern that such a launch would undermine stability in the region.

The United States has said the launch would cancel an agreement to send North Korea a large shipment of U.S. food aid in exchange for halting its nuclear and long-range missile programs.

Ahead of the summit, U.S. officials announced that Ukraine has completed the removal of a consignment of highly enriched uranium, which can be used to make nuclear bombs, following a two-year program with the United States and Russia. The material, Russian in origin, has been sent back to Russia.