WASHINGTON — When North Korea launched a small satellite into orbit last month for the first time, U.S. officials called it a cover for a more ominous goal: a ballistic missile that could carry a nuclear weapon as far as the continental United States.
But North Korea is a long way from building a workable intercontinental missile and, at the current pace of testing, it could take many years before they are close, missile technology experts say.
"They could put up something that would look like a credible missile but ... it's not really much of a threat," said Boston-based physicist David Wright, who follows the North Korean program for the nonpartisan Union of Concerned Scientists. "They have no idea whether it's going to blow up on the launch pad or dump one of their precious nuclear weapons into the Pacific Ocean."
This week, Bill Richardson, a former governor of New Mexico, is visiting Pyongyang, the North Korean capital, with Eric Schmidt, the executive chairman of Google, on what they are calling a private humanitarian trip. Richardson said Wednesday that he was pressing the government to stop all missile launches and nuclear tests and to allow more cellphones and an open Internet for its citizens.
Some experts outside the U.S. government contend that North Korea's failure-prone missile program is essentially a bluff aimed at spurring concessions from the international community.
U.S. intelligence officials disagree. They say North Korea is intent on developing a capability to threaten the West with nuclear weapons. In 2011, then-Defense Secretary Robert Gates said North Korea would have a missile that could strike the continental United States by 2016, although some U.S. officials believe that timetable has now slipped.
The North Koreans "haven't tested a lot, which slows development," said a U.S. official familiar with the latest intelligence. "But they're still moving forward."
North Korean leader Kim Jong Un hailed the Dec. 12 satellite launch in a televised New Year's Day speech, calling on the nation to rebuild its ailing economy "in the same spirit and mettle as were displayed in conquering space."
But progress has been halting. In recent years, North Korea has attempted one or two rocket tests annually, most of which failed. In April, a rocket carrying a satellite exploded 90 seconds after takeoff.
Building a dependable intercontinental ballistic missile would require "flight tests every other month, over several years," said Markus Schiller, who wrote a paper about the missile program in October for Rand Corp., a Santa Monica-based think tank. "First-generation long-range missiles require dozens of flight tests until they are reliable and accurate enough for deployment."
Schiller said in his Rand paper that the main purpose of the North's rocket launches is to deter the United States and South Korea, and "to gain strategic leverage in foreign politics."
The three-stage Unha rocket that put a small satellite into orbit last month "was developed as a satellite launcher and not as a weapon," Schiller said in a telephone interview from Germany. "The technology was only suited for satellite launch."
The rocket's third stage took a dog leg turn to avoid flying over Taiwan and the Philippines, said Brian Weeden, a former U.S. Air Force space expert now with the Secure World Foundation, a Washington think tank.
"That is definitely something more associated with a space launch than with a ballistic missile launch," he said. "It's not what you would expect to see with a missile test."
Any successful rocket launch could theoretically help North Korea improve its missile technology, Weeden said. But launching a satellite is easier than perfecting a missile that can carry a weapons payload into space and then deliver it to a specific target without burning up in the atmosphere.
Other analysts believe North Korea made a major technological advance with the satellite launch. Bruce Klingner, a former CIA analyst now at the Heritage Foundation, a Washington think tank, called it "a huge step forward in their capabilities."
Jeffrey Lewis, a nonproliferation expert at the nonpartisan Monterey Institute of International Studies, worries that North Korea is making just enough progress to be dangerous.
"The North Koreans might just be willing to deal with less reliable systems," he said. "They might just be happy with 50% reliability. My starting assumption is that they are serious, that this is something that they intend to build. I presume that they are competent enough that this is not an impossible missile."