China’s top nuclear experts have increased their estimates of North Korea’s nuclear weapons production well beyond most previous U.S. figures, suggesting Pyongyang can make enough warheads to threaten regional security for the U.S. and its allies.
The latest Chinese estimates, relayed in a closed-door meeting with U.S. nuclear specialists, showed that North Korea may already have 20 warheads, as well as the capability of producing enough weapons-grade uranium to double its arsenal by next year, according to people briefed on the matter.
A well-stocked nuclear armory in North Korea ramps up security fears in Japan and South Korea, neighboring U.S. allies that could seek their own nuclear weapons in defense. Washington has mutual defense treaties with Seoul and Tokyo, which mean an attack on South Korea or Japan is regarded as an attack on the U.S.
“I’m concerned that by 20, they actually have a nuclear arsenal,” said Siegfried Hecker, a Stanford University professor and former head of the Los Alamos National Laboratory, who attended the closed-door meeting in February. “The more they believe they have a fully functional nuclear arsenal and deterrent, the more difficult it’s going to be to walk them back from that.”
Chinese experts now believe North Korea has a greater domestic capacity to enrich uranium than previously thought, Mr. Hecker said.
The Chinese estimates reflect growing concern in Beijing over North Korea’s weapons program and what they see as U.S. inaction while President Barack Obama focuses on a nuclear deal with Iran.
A well-armed North Korea may prompt the U.S. to adopt countermeasures, especially in missile defense. Adm. William Gortney, head of U.S. Northern Command, said this month that defense officials believe North Korea can now mount a nuclear warhead on an intercontinental ballistic missile called the KN-08. U.S. officials don’t believe the missile has been tested, but experts estimate it has a range of about 5,600 miles—within reach of the western edge of the continental U.S., including California.
An increase in North Korea’s nuclear arsenal feeds international concern about proliferation from a country that, U.S. officials said, previously exported nuclear technology to Syria and missile components to Iran, Yemen and Egypt.
In Washington, some Republican lawmakers said the pending White House deal with Iran could mirror the 1994 nuclear agreement the Clinton administration made with North Korea. The deal was intended to halt Pyongyang’s nuclear weapons capabilities, but instead, they allege, provided diplomatic cover to expand them. North Korea tested its first nuclear device in 2006.
“We saw how North Korea was able to game this whole process,” U.S. Rep. Ed Royce (R., Calif.), chairman of the House Foreign Affairs Committee, said in an interview. “I wouldn’t be surprised if Iran had its hands on the same playbook.”
The pace of North Korea’s nuclear arms growth depends on its warhead designs and its uranium-enrichment capacity, Mr. Royce said: “We know they have one factory; we don’t know if they have another one.”
Recent estimates by U.S. experts range from 10 to 16 nuclear bombs today.
Mr. Royce said he met Chinese academics on a recent trip to Beijing and was struck by the concerns he heard about Pyongyang’s nuclear capabilities.
Relations between North Korea and China have deteriorated since Xi Jinping became China’s leader in 2012 and North Korea’s leader, Kim Jong Un, took power following the death of his father in late 2011.
China, which is North Korea’s largest investor, aid donor and trade partner, has for most of the past decade underestimated Pyongyang’s nuclear capabilities, nuclear experts said, including its capacity to produce fissile material.
Estimates of North Korea’s capabilities by Chinese experts began to align with those in the U.S. after 2010, and moved beyond after 2013, according to people familiar with exchanges on the matter between China and the U.S.
Until recently, the Chinese “had a pretty low opinion of what the North Koreans could do,” said David Albright, an expert on North Korea’s nuclear weapons and head of the Institute for Science and International Security in Washington. “I think they’re worried now.”
China’s foreign and defense ministries didn’t respond to requests for comment. Diplomats at North Korea’s mission to the United Nations didn’t respond to attempts to seek comment. The White House, State Department and Pentagon declined to provide U.S. estimates of North Korea’s nuclear arsenal.
“We have been and remain concerned about North Korea’s nuclear program and believe China should continue to use its influence to curtail North Korea’s provocative actions,” said Patrick Ventrell, a spokesman for the U.S. National Security Council.
He said the U.S. was working with other countries to implement U.N. sanctions designed to press North Korea “to return to credible and authentic denuclearization talks and to take concrete steps to denuclearize.”
The U.S. hasn’t engaged in regular high-level talks with Pyongyang since 2012, when North Korea conducted a long-range missile test. The U.S. has instead pressed China to use its economic leverage to rein in North Korea.
The latest Chinese estimates of North Korea’s nuclear capability were shared during a February meeting at the China Institute of International Studies, the Chinese foreign ministry’s think tank. The Chinese brought technical, political and diplomatic experts on North Korea’s nuclear program, as well as military representatives, said people familiar with the meeting.
Mr. Hecker, the U.S. team’s lead technical expert, has long been part of international efforts to understand North Korea’s nuclear program. In 2010, he revealed North Korea had a large uranium enrichment program after he saw the facilities during a visit there.
The estimate that North Korea may have had 20 warheads at the end of last year—and could build 20 more by 2016—was given during a presentation by one of China’s top uranium enrichment experts, according to people familiar with the meeting. They said it was the first time they had heard such a high Chinese estimate.
Mr. Hecker declined to comment on the meeting but said he had met with Chinese experts to discuss North Korea’s capabilities at least once a year since 2004.
“They believe on the basis of what they’ve put together now that the North Koreans have enough enriched uranium capacity to be able to make eight to 10 bombs’ worth of highly enriched uranium per year,” said Mr. Hecker, who added that estimates by China and the U.S. involved a great deal of guesswork.
U.S. officials didn’t attend the meeting but some expressed surprise when they were later briefed on the details, said people familiar with the matter. Some Chinese experts said the estimates revealed in February were at the higher range among local peers. Mr. Hecker said he estimated North Korea could have no more than 12 nuclear bombs now, and as many as 20 next year.
“Some eight, nine or 10 years ago, they had the bomb but not much of a nuclear arsenal,” he said. “I had hoped they wouldn’t go in this direction, but that’s what happened in the past five years.”