State Department spokesman John Kirby said at a regular briefing.

Kirby, however, declined comment on the North's shutdown of the "New York channel" that has long served as an important line of communication between the two sides that have no diplomatic relations.

"We call on North Korea to refrain from actions and rhetoric that only further raise tensions in the region. I'm not going to share the details of diplomatic exchanges one way or the other, but none of the rhetoric that we've seen of late is doing anything to increase security and stability on the peninsula," Kirby said.

"And the DPRK knows very well what its international obligations are and should know very well what their obligations are to its own people in terms of proper kinds of decisions and choices that they need to make going forward," he said.

Last week, the State Department released a report on the North's human rights situation, recommending sanctions against 15 top officials, including leader Kim, as well as eight state entities. Of them, the Treasury Department imposed sanctions on 11 officials and five agencies as the others have already been blacklisted for other reasons.

It was the first time the U.S. has imposed direct sanctions on the North's leader, and the designation also marked the first U.S. sanctions on Pyongyang over its human rights abuses. It showed the U.S. is committed to ratcheting up pressure on Pyongyang.

The North's Foreign Ministry reacted angrily to the sanctions, blasting the blacklisting as an "open declaration of war" and threatening to cut off all diplomatic channels with the U.S. unless the designation is revoked immediately.

U.S. experts said the North's reaction is not surprising.

"Pyongyang reacts strongly to any action directly affecting North Korean leadership. So in that respect, it is not unexpected that the North would adopt some sharp measures in response to the recently announced human rights-related sanctions naming Kim Jung-un," Alan Romberg, a distinguished fellow at the Stimson Center, told Yonhap News Agency.

"Although the New York channel has not proven particularly useful for the most part, if the DPRK sees it as in its interest to communicate with the United States, I'm sure it will find a way to do so," he said.

But Evans Revere, a former senior State Department official and currently senior adviser for the Albright Stonebridge Group, said the shutdown of the dialogue channel could be "disturbing and potentially dangerous."

"It has been years since the channel has functioned as an ongoing venue for serious bilateral exchanges and negotiations. But for many years the New York Channel has nonetheless played an important role by providing a communication, coordination, and logistical link between Pyongyang and Washington," he said. (Yonhap)