Therefore, submitting to foreign demands to give up its nuclear weapons could well mean more than humiliation and disgrace for North Korean leadership, and would mean delegitimization and destabilization for the regime as well, the expert said.

"Second, international entreaties -- summitry, conferencing, bargaining, and all the rest -- can never succeed in convincing the DPRK to relinquish its nuclear program. Sovereign governments simply do not trade away their vital national interests," he said.

Past nuclear deals with Pyongyang brought about US concessions, such as energy shipments and removal of the North from the terrorism sponsor list, but the "one thing 'engagement' can never produce, however, is North Korean denuclearization," he said.

Eberstadt also said that the notion of a "grand bargain" with Pyongyang, in which all mutual concerns are simultaneously settled, is "nothing but a dream."

The expert said the US should adopt a "threat reduction" approach to the problem, including significantly bolstering defenses against the North, such as deployment of the THAAD missile defense system in South Korea and Japan and beefing up the US missile defense systems.

He also called for sharply ramping up pressure on the North, including bringing an end to South Korea's "subsidized trade" with the North, putting the North back on to the US list of states sponsoring terrorism, and enforcing genuinely biting sanctions.

China should be forced to pay a penalty for all its support for the North, Eberstadt said.

Scott Snyder, chief Korea analyst at the Council on Foreign Relations, also told the Senate hearing that the window of opportunity to achieve North Korea's peaceful denuclearization may have closed, as the North's leader clings to the nuclear program as an internal justification for his rule.

"North Korea has decided, based on lessons from Iran, Iraq and Libya, that it must be too nuclear to fail," he said.

Snyder also said the North "lives in the space created by Sino-US geostrategic mistrust," and called for the US to impose "secondary sanctions" on Chinese entities that trade with the North.

He also suggested that the new administration appoint a senior envoy for North Korea who reports directly to the president as a way of signaling the urgency of the North Korea issue. (Yonhap)