WASHINGTON (Yonhap) -- The chief U.S. intelligence official Thursday did not rule out chances of North Korea provoking South Korea further after the North's attacks on a South Korean border island and a warship last year.

   Speaking at a Senate Armed Services Committee hearing, James Clapper, national intelligence director, said, "It is also our assessment at this time that there is a low probability of a conventional attack by the North upon the South."

   Clapper, however, added, "North Korea has shown a proclivity for doing sometimes the unexpected and it is the unintended consequences of those events that may precipitate something else."

   North Korea torpedoed the South Korean warship Cheonan and shelled Yeonpyeong Island, killing 50 people, including two civilians, chilling inter-Korean ties to the lowest level since the end of the 1950-53 Korean War.

   North Korea refused to apologize for the provocations and walked out of a rare inter-Korean dialogue last month, thwarting hopes for the resumption of the six-party talks on the North's nuclear dismantlement. The talks have been stalled over Pyongyang's nuclear and missile tests in 2009.

   Washington has called on Pyongyang to address Seoul's grievances over the deadly attacks before moving to a new round of the multilateral denuclearization-for-aid talks.

   Clapper said North Korea sees its nuclear arsenal as its only leverage.

   "With respect to North Korean intentions, obviously they continue to play their nuclear card," he said. "That is their single, I think, leverage point, or leverage device they can use to attract attention and seek recognition for them as a nuclear power."

   Lt. Gen. Ronald Burgess, director of the Defense Intelligence Agency, also told the hearing that North Korean leader Kim Jong-il's plans for power transfer to his youngest son, Jong-un, explain recent provocations.

   "Of significant concern is decision making relative to the apparent leadership succession under way and its implications for additional deliberate provocations against the South," Burgess said. "The North Korean artillery attack against Yeonpyeong Island on November 23, 2010, and torpedo attack on the naval corvette Cheonan on March 26, 2010, show Pyongyang's willingness to use military force to advance his external and internal goals.
Miscalculation could lead to escalation."

   The recent provocations are seen as part of the 28-year-old heir's effort to rally support from the military, just like his ailing father is suspected of masterminding the downing of a Korean Air plane in 1987 that killed all 115 passengers aboard.

   Kim Jong-il was being groomed at the time to succeed his father and North Korea's founder, Kim Il-sung, who died of a heart attack in 1994.

   Unlike Kim Il-sung, who was a guerrilla leader against Japanese colonialists, neither Kim Jong-il nor Jong-un has a proper background in the military, which serves as a linchpin for the impoverished communist state.

   North Korea, meanwhile, disclosed in November a uranium enrichment plant that could be used to make nuclear weapons apart from its plutonium program. The North claims its intention is to generate electricity.

   South Korea and the U.S. have said they will seek a U.N. Security Council presidential statement to condemn the uranium program before moving on to the nuclear talks involving the two Koreas, the U.S., China, Japan and Russia.

   China, North Korea's staunchest communist ally, wants the uranium issue to be dealt with at the six-party talks and opposes Security Council involvement, citing a possible adverse impact on an early resumption of the nuclear talks.