North Korea's de facto No. 2 figure expressed eagerness Thursday to bolster the country's nuclear capabilities, just days after it invited South Korean President Moon Jae In to visit Pyongyang for a summit.

"While firmly strengthening self-defense nuclear deterrence, we should develop and produce strong and advanced military equipment," Choe Ryong Hae, a key official of the ruling Workers' Party, said in a speech, according to state television channel KCTV.

But Choe, regarded as the right-hand man of North Korean leader Kim Jong Un, did not mention ties with the United States and recent moves toward improvement in relations with South Korea in the wake of the Pyeongchang Winter Olympics.

Choe made the speech a day before the anniversary of the birth of late leader Kim Jong Il, Jong Un's father.