Whiting said Pyongyang is preparing a second launch, after successfully putting a satellite into orbit last November.

"We are closely monitoring the DPRK's continued development and advancement of its space capabilities," he said after a two-day trip to South Korea.

Whithing, who has since traveled to Japan, held talks with South Korean officials about North Korea's ballistic missile capabilities.

In a virtual press conference, he also denounced Pyongyang's recent intercontinental ballistic missile launches, according to the Spanish news agency Europa Press.

Whithing said UN resolutions explicitly prohibit the use of ICBMs and called on North Korea to cease such launches.

North Korean leader Kim Jong Un on Monday oversaw a military drill simulating a "tactical nuclear" counterattack.

Pyongyang's renewed testing spree follows the collapse of a UN sanctions monitoring system on North Korea and its nuclear program due to a Russian veto in the Security Council.

In early April, North Korea said it had tested a new solid-fuel, medium- to long-range hypersonic missile.

Since the start of the year, North Korea has described South Korea as its "main enemy."

Pyongyang has shut down agencies dedicated to reunification and inter-Korean dialogue and threatened to go to war over any violation of its territory.

The Korean Peninsula in northeast Asia is divided between North and South Korea, which fought a war from 1950-53.

Pyongyang and Seoul remain technically at war, as they never signed a peace treaty, although an armistice halted the fighting.

In more than 75 years, the Democratic People's Republic of Korea (North) has had only three leaders: the regime's founder Kim Il Sung, who was succeeded by his son Kim Jong Il and, since 2012, his grandson Kim Jong Un.

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