North Korea is likely to be "exaggerating" claims that it successfully test-launched a ballistic missile from a submarine and miniaturized a nuclear warhead, a former U.S. intelligence chief said Friday.

Dennis Blair, former director of national intelligence, also slammed North Korean leader Kim Jong-un for being "very destabilizing, very dangerous," referring to a report by the South Korean spy agency that said Kim's defense minister had been purged and may have been executed.

North Korea has praised the recent test of a submarine-launched ballistic missile and boasted of its ability to miniaturize nuclear warheads. If confirmed, it would be a major breakthrough in the North's nuclear and missile capabilities, despite U.N. sanctions.

"I think that North Korea is exaggerating its technical achievement," Blair said in an interview with Yonhap News Agency in Beijing on the sidelines of an energy conference. "It certainly does not have a tested or demonstrated capability of those areas."

"But, nonetheless, North Korea does have nuclear materials. It certainly has unconventional delivery means. So, we have to think that it is a small-scale nuclear state," Blair said.

North Korea has conducted three nuclear tests so far and put an object into an orbit by launching a long-range rocket.

Blair, a retired admiral who also served as commander of the U.S. Pacific Command, said the North could carry out its fourth nuclear test "to try to exert pressure, to try to get concessions from South Korea, the United States, Japan, maybe from China."

To better cope with North Korea's nuclear and missile threats, both South Korean and U.S. officials have indicated the need for an advanced American missile-defense system in South Korea.

China, North Korea's economic lifeline and diplomatic backer, has publicly expressed its concerns over the possible deployment of the Terminal High-Altitude Area Defense (THAAD) battery to South Korea.

Asked about China's concerns over the U.S. missile-defense system, Blair replied, "I think China is wrong. Chinese missile experts are very knowledgeable. They know the THAAD system cannot be used to threaten the Chinese missile-defense system."

"The deployment is a decision for the Republic of Korea (South Korea) to make, based on its own reasons," Blair said.

South Korea and the U.S. have called for China to do more to rein in North Korea's nuclear and missile programs, but China's stance over its ideological ally, Pyongyang, has often been self-contradictory.  Many analysts believe that China's ruling Communist Party leadership won't put enough pressure on North Korea to give up its nuclear ambitions because a sudden collapse of the North's regime could threaten China's own security interests.

Blair acknowledged the role of China in curbing North Korean aggression, but said China's leverage on the wayward ally is also limited.

"I don't think that North Korea is paying any attention" to the Chinese calls for denuclearization," Blair said. "I think they are making their own decision." (Yonhap)