Why North Korea's latest nuclear test has experts especially worried

North Korea's nuclear test this month was its fifth in only 10 years, but technological advances by the isolated communist state have former diplomats concerned that the latest blast is anything but more of the same.

Only eight months passed between North Korea's most recent test and its fourth, held in January, and that tight time frame indicates the country is accelerating its development of nuclear weapons, said Ambassador Sung-hwan Kim, South Korea's former minister of foreign affairs and trade. The amount of time that passed between the first four tests ranged between 31 months and 44 months.

Kim spoke along with a group of other experts, most of them former diplomats, at the Asia Society in New York on Monday night.

Aside from the faster weapons development, the panel pointed to a number of other relatively new developments:

• North Korea is getting closer to standardizing its nukes, which could make mass production possible.
  

• The country's nuclear weapons are getting smaller.

• It's now developing longer-range rockets that could be used to attack the U.S.

• It's working on solid-fuel rockets, which can be prepared and launched on shorter notice than liquid-fuel rockets.

North Korea's nuclear program has bedeviled four U.S. presidential administrations going back to at least 1991, when the North and South agreed to ban nuclear weapons from the Korean Peninsula. Within a couple years, North Korea began advancing its development of nuclear devices and missiles, in fits and starts at first but more consistently as time went by.

Part of the reason the situation with North Korea has been allowed to escalate over the years is that the U.S. and South Korea have hoped that the North Korean regime would eventually implode on its own. That hasn't happened.

"We have done wishful thinking that North Korea would collapse, and this has shaped our negotiations with them," said Chung-in Moon, distinguished professor emeritus at Yonsei University and former South Korean ambassador for international security affairs. "We must face reality."

All the panel members agreed that China has to play a large role in fixing the problems on the Korean Peninsula. The world's second-largest economy is North Korea's biggest trade partner by far and its only ally. But it has not pressured North Korea — at least not publicly — to rid itself of nuclear weapons.

"We need to find out what China's real worries are, and find an end-game they like," said Christopher Hill, who led the U.S. delegation to the Six Party Talks on North Korea's nuclear program while he served as assistant secretary of state for East Asian and Pacific affairs.

Part of the challenge with China, however, is that it doesn't agree with the U.S. on what the main problem is, said Yun Sun, an expert on Chinese foreign policy who works as senior associate with the East Asia Program at the Henry L. Stimson Center.

She said the U.S. sees North Korean nukes as the primary threat in the region, but China is more afraid of having U.S. troops on its border if the North Korean state were to collapse and, presumably, end up folded into a unified Korea that's dominated by the South.

Multiple panel members even raised the possibility that North Korea may use its nukes to threaten China.

The panel debated a number of possible ways to address the crisis, none of which seemed satisfactory to the entire group during what became at times a lively discussion.

Options included so-called secondary sanctions, which punish countries outside North Korea that do business with or otherwise assist the country; various levels of military deterrence against North Korea; and the possibility of the U.S. trying to ease tension by canceling the planned deployment of a missile defense system to South Korea.

South Korea's Moon and former U.S. Ambassador Hill agreed that the United States has to lead the region to a resolution.

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