North Korea's announcement that it will launch a controversial rocket is upstaging an international nuclear summit in Seoul, South Korea.
The communist country said it will launch a satellite into space next month aboard a long-range rocket. It said it's for peaceful purposes.
The same technology, however, could also deliver a nuclear warhead. President Obama is urging North Korea to forego its plans.
"There will be no rewards for provocations. Those days are over. Today we say Pyongyang have the courage to pursue peace and give a better life to the people of North Korea," he said.
South Korea and other countries are warning the North they might shoot down the rocket if it strays into their territory.
President Obama said if the North launches this rocket, the U.S. will withhold desperately needed food aid.
"You can continue down the road that you are on, but we know where that leads -- at least to more of the same, more broken dreams, more isolation," Obama said.
Meanwhile, North Korea said it will consider criticism of its nuclear program at the summit to be a "declaration of war."
The drama over its rocket is taking attention from the summit's original plan to lock down the world's supply of nuclear material by 2014.
President Obama is also scheduled to meet with Russia's leaders this week to talk about reducing both U.S. and Russian stockpiles of nuclear warheads.
"We have more nuclear weapons than we need. I firmly believe that we can ensure the security of the United States and our allies," Obama said.
The president will also press the issue of Iran in one-on-one meetings with the leaders of Russia and China. He's hoping to use the summit to pressure Iran to halt its suspected nuclear weapons program.