Kim started the press conference praising the North's successful ballistic missile launch last weekend, which experts said demonstrated a significant technological jump with the rocket flying higher and for a longer period of time.
The comments came hours after the South, which hosts 28,500 United States troops, said it wanted to reopen a channel of dialogue with North Korea as Moon seeks a two-track policy, involving sanctions and dialogue, to try to rein in its neighbour.
At the Pentagon, Defense Secretary Jim Mattis said the missile test showed North Korea isn't heeding cautions from the worldwide community.
"As everybody knows, the Americans have gestured [toward] dialogue", Deputy UN Ambassador Kim In Ryong told reporters Friday, as cited by Reuters.
"The rolling back of the hostile policy towards DPRK is the prerequisite for solving all the problems in the Korean Peninsula", he said.
Mr Mattis said: "We are going to continue to work the issue".More news: Murray stunned but Djokovic makes last 8
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On China's opposition to the deployment of the U.S. THAAD missile defense system in South Korea, Tillerson said Beijing appears to be relaxing sanctions it imposed on the South Korean conglomerate Lotte Group that provided land for the THAAD battery. The North also probably has a way to go before it can miniaturize a nuclear warhead to mount on such a missile.
Speaking at the United Nations headquarters in New York City, the Democratic People's Republic of Korea's deputy U.N. ambassador flatly denied Pyongyang played a part in last week's unprecedented cyberattack, dismissing suspicions raised recently by security researchers in the USA and overseas.
Meanwhile, the South Korean Navy revealed a USA nuclear-powered aircraft carrier group was to remain in the vicinity indefinitely, while Seoul's defense ministry warned it was ready to carry out a preemptive strike if it detected a missile threat from North Korea. A U.S. State Department spokesman said the United States remains open to talks with North Korea but the country would have to "cease all its illegal activities and aggressive behavior in the region".
If the United States "persists in anti-DPRK sanctions without understanding its rival, the (Trump) administration will have to take full responsibility for the ensuing catastrophic consequences", he warned.
"The U.S. should mind that the DPRK nuclear striking capability will be strengthened and developed at a rapidly high speed as long as the U.S. insists its anti-DPRK policy, nasty nuclear threats and blackmails, sanction and pressure", he said.