ROBERT SIEGEL, HOST:
As we just heard, the big concern here isn't just for this long-range rocket launch. It's that North Korea will follow the launch with another underground nuclear test. The pattern was established three years ago. But this time around, Pyongyang may have a more urgent need for such a test.
As NPR's Mike Shuster reports, the bomb is likely the result of a significant expansion of its weapons program.
MIKE SHUSTER, BYLINE: One big difference between the last long-range rocket test in 2009 and the one this week, is that North Korean officials are talking about it and actually answering reporters' questions. Just a few days ago, they brought international correspondents to the rocket launch site in northwestern North Korea, let TV cameras take pictures of the rocket on the launch pad, as well as a device they said was the weather satellite they want to put into orbit.
The director of the launch site, Jang Myong-jin, dismissed suspicions that the rocket launch is really a disguised military missile test.
JANG MYONG-JIN: (Through Translator) If it were a ballistic missile, it would have to be hidden in an underground chamber, or it would need to be carried on board another vehicle for protection. If it were not, then it would be useless in a real war.
SHUSTER: Many North Korea watchers argue that North Korea's effort to construct an effective three-stage rocket or missile is meant ultimately to reach targets in the United States. Other experts believe the North Koreans have American targets in mind, but closer to Korea, in case of war.
Dan Sneider, of Stanford University's Asia Pacific Research Center, believes this is consistent with North Korean plans to prevent U.S. air and ground forces stationed in Okinawa and Guam from defending South Korea.
DAN SNEIDER: Their missile program, at least as they conceived of it early on, was intended to sort of neutralize the ability of the United States to intervene from bases in Japan, in support of the South Korean army.
SHUSTER: North Korea does not have an effective air force that could challenge U.S. air power in an actual conflict, so it looks to its missiles to do that job, says Sneider.
SNEIDER: So I think it's much more important to them, much more logical for them, to try and put at threat U.S. forces in the region. Not to, you know, seriously threaten the United States with an intercontinental ballistic missile.
SHUSTER: At the same time, activity has been detected at North Korea's underground nuclear test site in the northeast of the country, suggesting preparations for another nuclear test are underway.
North Korea has carried out two nuclear tests in the past, both using plutonium bombs. Neither test was especially successful, experts say. But North Korea stopped producing plutonium several years ago, and turned to uranium enrichment, under production at the nuclear complex at Yongbyon.
At the same time, its likely North Korean engineers have been working to build a warhead that could be carried on a missile, like the one currently on the launch pad.
Daryl Kimball, the director of the Arms Control Association in Washington, says all these reasons make the case for the North Koreans to carry out another test.
DARYL KIMBALL: Before they deploy such a weapon, especially on a ballistic missile, I would think that their scientists and engineers, and the military, would want to proof-test that device. There are simple designs that can be built and one can be quite confident that they will explode without nuclear testing. But in order to put a smaller device on a ballistic missile, most military planners would want to have a nuclear explosive proof-test.
SHUSTER: In the past, North Korea has warned the West that it would carry out a test if it were chastised by the U.N. Security Council or new sanctions imposed.
Dan Sneider views claims like that as a smokescreen.
SNEIDER: I don't think a third nuclear test would be a response to sanctions that are imposed. I think that's probably something that they've been planning for a long time.
SHUSTER: It's this pattern of activities, including ongoing production of highly enriched uranium, that most worries Daryl Kimball.
KIMBALL: One ballistic missile test launch is a problem. A ballistic missile test launch followed by a nuclear test explosion, followed by uranium enrichment at Yongbyon and facilities probably beyond Yongbyon is a much more significant problem.
SHUSTER: But that appears to be the very path North Korea is on at the moment.
Mike Shuster, NPR News.