The North's leader has stepped up preparations to bequeath power to the youngest son still believed in his 20s.

In September, the totalitarian regime made the junior Kim a four-star general and gave him high-level posts in the ruling Workers' Party. The moves represented the North's first concrete steps to put the inexperienced son in line to take over the family dynasty.

The DNI chief said, however, that the "succession process is still subject to potential vulnerabilities, especially if Kim Jong-il dies before Jong-un consolidates his authority."

On the North's nuclear capabilities, Clapper said that the communist regime is believed to have tested two nuclear devices. It is still unclear "whether the North has produced nuclear weapons, but we assess it has the capability to do so."

Fueling concern about the North's nuclear capabilities were Pyongyang's revelations in November that it has a uranium enrichment facility at the country's main Yongbyon nuclear complex.

Uranium, if highly enriched, can be weapons-grade, providing the regime with a second way of building atomic bombs after the existing plutonium-based program.

Clapper said the North must have been seeking uranium enrichment for an "extended period of time."

"If so, there is clear prospect that DPRK has built other uranium enrichment-related facilities in its territory, including likely R&D and centrifuge fabrication facilities, and other enrichment facilities," he said.

In recent months, North Korea has indicated a growing willingness to return to the nuclear negotiating table, reversing its previous stance that it will never come back to the six-party nuclear talks that were last held in December 2008.

"The North probably wants to resume nuclear discussions to mitigate international sanctions, regain international economic aid, bolster its ties with China, restart bilateral negotiations with South Korea and the United States, and try to gain tacit international acceptance for its status as a nuclear weapons power," the U.S. spy chief said.

The North's conventional military capabilities have weakened significantly over the past 10-15 years due to "persistent food shortages, poor economic conditions, inability to replace aging weapons inventories, reduced training, and increased diversion of the military to infrastructure support."

Still, the North's military "remains a large and formidable force" and "is capable of conducting military operations that could potentially threaten regional stability. These operations provide Pyongyang with what the regime may see as a means to attain political goals through coercion," Clapper said.

(Yonhap News)