A South Korean intelligence report says North Korea is preparing to test a nuclear weapon, as the isolated communist regime readies the launch of a long-range rocket as early as this week.
Analysis of satellite imagery shows tunnels being dug at the Punggye-ri nuclear test site, where atomic tests were conducted in 2006 and 2009, according to the intelligence report. The document was the subject of a report Sunday by South Korea's Yonhap news agency.
Work at Punggye-ri is believed to be in its final stages, Yonhap said, citing unnamed intelligence officials.
The satellite pictures, shown on South Korean TV news, revealed large piles of earth and sand at the entrance to a tunnel on the site. Analysts believe the soil was brought to the site to fill in the tunnel, one of the last steps before test-firing a nuclear weapon underground.
The news will raise tensions on the divided peninsula, where 28,500 U.S. troops and their South Korean allies face off against their North Korean counterparts across the last Cold War border.
Previous nuclear tests followed within three months of a multistage rocket launch, like the one Pyongyang has announced will take place between Thursday and Monday. Washington officials say the rocket has the range to hit parts of the United States.
On Monday, several Asian airlines said they would reroute flights in the region to avoid the area around the rocket's projected flight path. Last week, Japan and South Korea announced that they would shoot down any parts of the rocket that threatened to fall onto their territories. North Korea said that would be an act of war.
Over the weekend, the normally secretive North Korean regime took the extraordinary step of admitting a group of escorted foreign reporters to the Sohae Satellite Station in the far northwest of the country.
The reporters were shown the three-stage Unha-3 long-range rocket, which appeared to be fully assembled on the launchpad, and the communications satellite Pyongyang says it will carry.
Officials at the site insisted that the launch - part of the celebrations this week of the centenary of the country's founder, Kim Il-sung - is peaceful and legal. They said every sovereign nation has the right to the peaceful exploration and use of space.
U.S., Japanese and South Korean officials say the launch will test long-range missile technology, violating a U.N. ban on North Korean ballistic and nuclear weapons development.
"They can't launch the thing without using ballistic missile technology, which is precluded by U.N. Security Council Resolution 1874," State Department spokeswoman Victoria Nuland said Monday. "So, regardless of what they say about it, it's still a violation."
She called the launch "highly provocative" and said a nuclear test "would be equally bad, if not worse."
White House spokesman Jay Carney said the rocket launch would "make it virtually impossible" for the United States to provide planned food aid to North Korea's dangerously malnourished population.
Ms. Nuland said the United States is continuing to reach out to Japan, Russia, South Korea and, most important, China, which is North Korea's major trading partner and only ally. Those countries have been involved with North Korea and the United States in six-party talks over the North's nuclear program.
Over the weekend, Chinese Foreign Minister Yang Jiechi said he is "concerned and worried" about developments on the Korean Peninsula, according to Beijing's official Xinhua News Agency.
Nevertheless, North Korea appeared determined to push ahead with the launch.
None of its previous three rocket tests, in 1998, 2006 and 2009, was completely successful, said Victor Cha, East Asia director for the National Security Council in the George W. Bush administration.
"But each one was more successful than the last," he said.
Even a partially successful test this time would demonstrate that North Korea "has the technology to make a missile that can reach part of the United States," said Mr. Cha, now a scholar at the Center for Strategic and International Studies in Washington and the author of a recent book about North Korea.
The new rocket is assessed to have a maximum potential range of more than 4,160 miles. At its closest point, Alaska is about 3,100 miles from North Korea.
In 2006, the regime carried out its first nuclear test, three months after test-firing the long-range Taepodong-2 rocket. The second nuclear test was in May 2009, one month after the launch of another long-range rocket, the Unha-2. Within a year, a North Korean submarine had sunk a South Korean warship.
"The provocations are getting closer together," Mr. Cha said.
"A likely scenario," he said, is that North Korea would use international condemnation of the illegal launch "as justification for a third nuclear test."
The Obama administration had few good policy responses available to either the scheduled rocket launch or a nuclear test, Mr. Cha said.
"It's a tough position to be in," he said.
He predicted that the administration would face criticism for reopening talks after the last pair of tests in 2009, if the launch proceeds.
"It's hard to go back to talks after they've done something like that, but there aren't really any military options either," he said.
Covert action against the tests or the ballistic or nuclear weapons program, like that the administration has launched against Iran, would be "very high risk."
"North Korea is truly the land of lousy options," Mr. Cha said.
• This article is based in part on wire service reports.
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