The U.S. government is tracing funds owned by North Korean leaders as part of sanctions on the communist country Washington is expected to announce soon.

State Department spokesman Philip Crowley told a regular news briefing that the U.S. is monitoring the transactions of money owned by North Korean leaders.

He made the remark in response to a report which said North Korean leader Kim Jong-il may be transferring four billion U.S. dollars of his slush funds to one of his sons.

In relation, a diplomatic source said that North Korean figures who will likely be subject to the new U.S. sanctions include Ri Je-son, head of the North's General Bureau of Atomic Energy; Namchongang Trading Corporation director Yun Ho-jin; and North Korean leader Kim Jong-il’s brother-in-law Jang Song-thaek.