Defying warnings from the international community, North Korea launched a long-range rocket on Friday, but it broke apart before escaping the earth's atmosphere and fell into the sea, officials said.

"It flew about a minute, and it flew into the ocean," said Noriyuki Shikata, a spokesman for Japanese Prime Minister Yoshihiko Noda.

He added that Japanese authorities "have not identified any negative impacts, so far," though he said the international ramifications could be significant. "This is something that we think is a regrettable development," he said.

Joseph Cirincione, president of the global security foundation The Ploughshares Fund, told CNN that the launch's apparent failure "shows the weakness of the North Korea missile program" and suggests that the threat from North Korea has been "exaggerated."

"It's a humiliation," he told CNN. "I wouldn't want to be a North Korean rocket scientist today."

In an unusual admission of failure, the North Korean state media announced that the rocket had not managed to put an observation satellite into orbit, which Pyongyang had insisted was the purpose of the launch.

In the past, North Korea has insisted that failed launches have been successful.

"Scientists, technicians and experts are now looking into the cause of the failure," the official Korean Central News Agency said in a report, which was also read out in a news broadcast on state-run television.

Just hours after the United States warned that North Korea would achieve nothing with threats or provocations, Pyongyang moved a long-range rocket it plans to test fire to a launch pad Monday, a South Korean defense ministry official said.

The news broke at the start of a two-day nuclear summit in Seoul that is bringing together leaders from the United States, Russia, China and dozens of other nations to discuss how to deal with nuclear terrorism and how to secure the world's nuclear material.

But North Korea's announcement that it plans to carry out a rocket-powered satellite launch in mid-April is overshadowing a message of international cooperation for the summit.

South Korea has said it considers the satellite launch an attempt to develop a nuclear-armed missile, while U.S. President Barack Obama said Monday such a launch would bring repercussions.

"Here in Korea, I want to speak directly to the leadership in Pyongyang. The United States has no hostile intent toward your country," Obama said during a speech to students at Seoul's Hankuk University of Foreign Studies.

"But by now it should be clear, your provocations and pursuit of nuclear weapons have not achieved the security you seek. They have undermined it."

If the rocket is launched, South Korea is prepared to "track its trajectory," said the defense ministry official, who did not want to be named.

"There are concerns that parts of the rocket may fall within South Korean territory," he said. "If that were to happen it would threaten lives and cause damage to the economy. To guard against that, they (the military) will be tracking the orbit."

The official did not say what steps South Korea would be forced to take if it determined the rocket was falling within its territory.

The rocket was moved to a launch pad in the northeastern portion of Dongchang-ri, a village in northwest North Korea, the official said.

North Korea announced plans Friday to blast a satellite into space on the back of a long-range rocket, a provocative move that could jeopardize a weeks-old agreement with the U.S. exchanging food aid for nuclear concessions.

The North agreed to a moratorium on long-range launches as part of the deal with Washington, but it argues that its satellite launches are part of a peaceful space program that is exempt from any international disarmament agreements. The U.S., South Korea and other critics say the rocket technology overlaps with belligerent uses and condemn the satellite program as a disguised way of testing military missiles in defiance of a U.N. ban.

[Related: U.S. condemns satellite plans]

The launch is to take place three years after a similar launch in April 2009 drew widespread censure.

Japan urged Pyongyang to abandon the latest launch, calling it a violation of a U.N. resolution restricting the North's use of ballistic missile technology, and South Korea called the plans a "grave provocation."

The liftoff is slated for between April 12 and 16 from a west coast launch pad in North Phyongan province to test satellite technology, a spokesman for the Korean Committee for Space Technology said in a statement carried by state media.

The plan comes as North Korea prepares to celebrate the April 15 centenary of the birth of its founder, Kim Il Sung. Kim's grandson, Kim Jong Un, has led the nation of 24 million since his father, Kim Jong Il, died in December.