Why the Political Bureau, which Kim Jong Un heads, called the congress has triggered speculation. They were once more common but ceased once his father took power.

"We do expect some kind of big announcement at the party congress, most likely some kind of economic policy," said Jenny Town, assistant director of the U.S.-Korea Institute at the Johns Hopkins School of Advanced International Studies.

She said that he has a "dual track" of military and economic advancement to make good on and has been "hyper-signaling" the country's advances in nuclear capabilities, so can now focus on economic development.

"It would be a positive direction but miscalculated, because even if they've been hyper-signaling their nuclear capabilities only for domestic propaganda purposes, it will be difficult to make good on economic promises," given the country's economic climate, amid wide-ranging sanctions and poor relations with its sole regional ally, China.

Consolidating power?

The congress may be intended to bolster the perception that Kim has a stable hold on power, Yang Moo-jin from South Korea's University of North Korean Studies said when it was first announced. Kim may announce economic reforms or new diplomatic relations.

Or it could reflect a shift in internal power from the military to the party.

"When Kim Jong Il was in power...the 'National Defense Commission' played a key-role in state affairs. The holding of the 7th Congress could symbolize that the Worker's Party's role was normalized. One of the key things to watch is whether Kim Jong Un will maintain the 'National Defense Commission' system or shift the function back to the party," Yang said.

On Sunday, it commemorated the 84th anniversary of the founding of the Korean People's Army, the armed forces of the Workers' Party of Korea with a "national meeting," according to North Korean state media.

North Korea practices its own brand of communist ideology called Juche, which propagates nationalist self-reliance as opposed to internationalism, which is a core principal of Marxist-Leninist communism.

"We call on North Korea to refrain from actions that further destabilize the region and focus on what it needs to do, which is take concrete steps toward fulfilling its commitments and its obligations to denuclearize," U.S. State Department spokesman Mark Toner said Tuesday.