WASHINGTON (Reuters) - North Korea likely is closer to mounting nuclear warheads on its ballistic missiles than generally reported, possibly only one or two years away, the Congress's former top expert on the issue has concluded.
Larry Niksch, who tracked North Korea for the nonpartisan Congressional Research Service for 43 years, concludes in a new paper that the North probably would need as little as one to two years to miniaturize and mount a nuclear warhead atop its medium-range Nodong missile once it has produced enough highly enriched uranium as the warhead's core fuel.
A North Korea armed with nuclear-tipped missiles would rattle East Asia and present new policy and military challenges to the United States and its allies.
Trying to determine when Pyongyang will reach that threshold has long been a challenge for the U.S. intelligence community. Niksch's timeline, if correct, puts out a new marker for strategists.
Last January, then-U.S. Defense Secretary Robert Gates said the North was within five years of building an intercontinental ballistic missile that, paired with its nuclear program, would be "a direct threat" to the United States.
North Korea has staged relatively few missile tests in recent years, suggesting it is still working on perfecting the needed technologies even as it has cooperated with Iran to do so.
Its nuclear and missile capabilities are once again in the spotlight as power passes to North Korea's designated young leader, Kim Jong-un, after the December 17 death of his father, Kim Jong-il.
Pyongyang already may have produced enough highly enriched uranium (HEU) for a warhead or be close to doing so, Niksch and experts such as Siegfried Hecker, the former head of the Los Alamos National Laboratory, said in interviews with Reuters.
Hecker said the North would have to conduct another nuclear test, its third, to have confidence that it had successfully miniaturized a warhead for one of its missiles.
"If the test is successful they may be able to have the capability within a couple of years," he said in an email exchange, referring to a nuclear-tipped missile.
"We simply don't know what else they have and how much HEU they can make or have made," added Hecker, who toured North Korea's Yongbyon nuclear complex in November 2010, his fourth visit there.
Jonathan Pollack, author of the 2011 book No Exit: North Korea, Nuclear Weapons, and International Security, emphasized the many unknowns pending further North Korean nuclear and missile tests.
"I think they'd have a reasonable chance of being able to mount a nuclear warhead on a missile in three to five years if they speed up research, development, testing and evaluation," said Pollack, of the Brookings Institution in Washington.
"If North Korea achieves some testing successes earlier than I anticipate, it might able to achieve this goal somewhat sooner."
The North is reckoned by U.S. intelligence to have between 30 and 50 kilograms of separated plutonium, enough for at least half a dozen nuclear weapons. Plutonium is the other type of fissile material used in nuclear weapons.
Pyongyang apparently has decided against making more plutonium bombs since it shut down a plutonium production facility at its Yongbyon nuclear complex in July 2007. It did so during six-party nuclear disarmament talks that it has since abandoned.
The North may have several plutonium-based nuclear warheads small enough to be mounted on missiles as well as dropped from aircraft, Lieutenant General Ronald Burgess, director of the U.S. Defense Intelligence Agency, told the Senate Armed Services Committee March 10.
Even with limited HEU production of which the North may already be capable, it could generate enough new bombmaking ingredients for one to two weapons per year, nuclear scientists say.
The North has been pursuing nuclear and missile capabilities for strategic deterrence and international prestige as well as for economic and political concessions, Burgess told Congress.
"While North Korea may be willing to abandon portions of its nuclear program in exchange for improved relations with the United States, Pyongyang is unlikely to eliminate its nuclear weapons," he said.
The Defense Intelligence Agency declined to comment for this article on its estimate for a nuclear-tipped missile, as did the CIA. Non-government experts emphasized the difficulty of pinning down nuclear developments in North Korea, a country distinguished by its opaqueness.
The North has conducted two tests of a nuclear device, in October 2006 and in June 2009. It has carried out three tests of missiles beyond medium range since 1998. The sole test of its intermediate-range Taepodong-1 overflew Japan and landed in the Pacific in August 1998, falling short of a declared goal of putting a satellite into orbit. But it spurred perhaps billions of dollars of Japanese investment in U.S.-built antimissile hardware and defense services.
The maiden flight test of North Korea's longest-range missile, the Taepodong-2, ended in failure about 40 seconds after launch on July 5, 2006. It was tested again in April 2009, when its first stage traveled about 270 km before falling into the Sea of Japan without orbiting a small communications satellite.
Niksch predicted North Korea first would mount nuclear warheads on its Nodong and shorter-range Scud missiles, possibly followed by mating them to long-range missiles. He said this would fuel domestic pressure in Japan to develop long-range strike capabilities despite its war-renouncing constitution, and rattle the region.
Japan on Monday urged China -- host of the talks that also involved the two Koreas, Russia, Japan and the United States -- to shoulder a big role in making sure that North Korea avoids volatile moves after its announcement of Kim Jong-il's death of a heart attack, apparently at age 69.
Constraining North Korea is especially important for Japan, which is well within range of the North's long-range missiles.
Niksch's one- to two-year timeframe for mounting a nuclear warhead is based largely on his assessment of reports about warhead technology shared with Pyongyang by A.Q. Khan, regarded as the father of Pakistan's nuclear bomb.
Niksch said in the interview "there can be no doubt" that North Korea received from Khan a blueprint of the nuclear warhead mounted on Pakistan's medium-range Ghauri missile.
But Pollack said he did not put much faith in accounts based on information supposedly supplied by A.Q. Khan, a nuclear scientist considered by experts, including Hecker, as an unreliable source.
Pakistan's Ghauri itself is a twin of Nodong missiles supplied by North Korea before May 1998, when Pakistan tested its first nuclear devices. Pakistan mounted nuclear warheads on its Ghauri missiles within three years, Niksch said in a paper to be published Friday by the Institute of National Security Strategy in Seoul.
North Korean nuclear experts were present at six nuclear tests that Pakistan carried out in May 1998 and the North "appears to have received all of the test data," said Niksch, now an advisor to the Washington-based Center for Strategic and International Studies.
Hecker, who from 1986 to 1997 headed the Los Alamos National Laboratory that handles U.S. military nuclear research, was shown what he has called "astonishingly modern" uranium enrichment facilities during his November 2010 tour of the Yongbyon complex.
The facilities are likely configured to make low enriched uranium for the experimental light-water reactor that he was shown but they could be "readily converted to produce highly enriched uranium bomb fuel," he said in his trip report.
The North must have additional centrifuge facilities to have made as much progress in such a short time, including some that may be dedicated to producing HEU bomb fuel, Hecker added in the email exchange.
HEU contamination was found by U.S. scientists on aluminum samples and copies of reactor operation documents provided by North Korean officials to U.S. authorities while the six-party talks were progressing, said Hecker.
Bruce Lemkin, who from 1997 to 2000 negotiated in and with North Korea on behalf of the U.S. Joint Chiefs of Staff and the Korean Peninsula Energy Development Organization, predicted a dramatic show of military power soon, to "validate" the leadership of Kim Jong-un, who has been picking up new titles in an apparent attempt to signal a power consolidation.
"Perhaps it will be another nuclear test detonation or a ballistic missile firing or both, perhaps even with the assertion that North Korea has, indeed, weaponized similar missiles with nuclear devices," said Lemkin, who retired in 2010 as U.S. Air Force deputy undersecretary for international affairs.
U.S. officials have a habit of underestimating the North Koreans, Niksch said.
"They tend to make more rapid advances in expanding their nuclear weapons program than U.S. experts believe they are capable of," he said.
Editing by Warren Strobel and Christopher Wilson