North Korea could conduct another nuclear test before a key party congress early next month, to show off its "full nuclear weapon status" and bolster its leader Kim Jong-un's legitimacy, a prominent U.S. expert said Wednesday.

In an interview with reporters, Victor Cha, senior North Korea analyst at the U.S.-based Center for Strategic and International Studies, also noted the "secondary sanctioning" to punish third-country entities doing business with the North would be the most impactful measure that can be imposed in the event of Pyongyang's fifth nuclear test.

"It wouldn't surprise me if we saw a fifth nuclear test before the party congress. But I do think that most of the sorts of provocations are largely going to be only WMD-type provocations," he said on the sidelines of the Asan Plenum 2016, an annual forum hosted by the Asan Institute for Policy Studies.

"I think the driver of these provocations is a desire to demonstrate to their own people and to the world that they have achieved a full nuclear weapon status before the party congress to give legitimacy to Kim Jong-un."

Pyongyang is gearing up to hold the rare congress of its ruling Workers' Party starting May 6, a crucial political gathering in which Kim is expected to flaunt the communist regime's political, military, ideological and economic achievements, and put forward the country's future direction.

Depicting the North Korean leader as being "unpredictable and showing little restraint," the scholar said should Pyongyang press ahead with another nuclear test, the "secondary sanctioning" that could potentially target Chinese companies will have the "most impact."

He pointed out that although Washington has set up the authority for the third-country sanctions following the North's fourth nuclear test in January, it has yet to exercise the authority that would put great pressure on the wayward regime.

"They set up the authority that they haven't exercised yet. I think after a fifth nuclear test, they will exercise that authority even if it is against Chinese companies," he said.

Referring to the concerns that the sanctioning of Chinese companies would undermine relations between Washington and Beijing, Cha claimed that the secondary sanctioning would not be a "big deal." 

He said only small Chinese companies that do business with the North would be subject to the sanctions given that most of the big Chinese companies have already suspended transactions with the North.

"I know everybody makes a big deal about the secondary sanctioning, but I really don't think it is going to be that difficult," he said.

Touching on the North Korean leader scrambling to establish his governing legitimacy, Cha said that the isolated state is now caught in a "legitimacy spiral" in which the unpredictable leader is exploring ways to build his political credentials based on the nuclear power or economic development.

"North Korea may want to base the legitimacy of Kim Jong-un on economic growth, the quality of life, but they have been unsuccessful in doing that. So they increasingly need to rely on the nuclear weapons as a primary matrix for legitimacy," he said.

"But the more they rely on nuclear weapons, the more sanctions they will get, which makes it harder for them to do economic development, which means they need to focus more on their nuclear weapons."

Portraying the spread of private market places in the North as the "single most important change" that has ever happened over the past two decades, Cha warned that Pyongyang would face a "severe" reaction should it move to control it.

He pointed out that the growing private economy is a double-edged sword as it could help sustain the impoverished country but could pose a "destabilizing" challenge to the despotic regime. (Yonhap)