U.S. President-elect Donald Trump's "clear warning" to North Korea shows he is aware of the urgency of the threat posed by its nuclear program and will not waver from a policy of sanctions against the isolated country, South Korea said on Tuesday.
North Korean leader Kim Jong Un said on Sunday his nuclear-capable country was close to test-launching an intercontinental ballistic missile (ICBM), raising the prospect of putting parts of the United States in range.
Trump dismissed the claim, saying on Twitter: "It won't happen."
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South Korea's foreign ministry said Trump's comment, his first mention of the North Korean nuclear issue since the U.S. election in November, could be interpreted as a "clear warning" to the North.
"Because of our active outreach, President-elect Trump and U.S. officials are clearly aware of the gravity and urgency of the North Korean nuclear threat," ministry spokesman Cho June-hyuck told a briefing.
"They are maintaining an unwavering stance on the need for sanctions on North Korea and for close cooperation between South Korea and the U.S.".
Trump has not outlined a policy on North Korea but during the U.S. election campaign indicated he would be willing to talk its leader, Kim, given the opportunity.
He has also been critical of China over the issue. On Monday, Trump said China had benefited from its economic ties with the United States but would not use its influence to help control North Korea.
Responding to the comment, Chinese Foreign Ministry spokesman Geng Shuang said China had been pushing for the denuclearization of the Korean peninsula.
"China's efforts in this regard are perfectly obvious," Geng told a news briefing. "As a permanent member of the UN Security Council we have proactively participated in relevant discussions on the North Korean nuclear issue and have jointly passed several resolutions with other parties.
"This shows China's responsible attitude".
The United States has for years dismissed North Korean calls for talks, insisting it must disarm first.
Instead, the United States and ally South Korea have responded to two North Korean nuclear tests and various missile tests last year with ever-more severe sanctions.
The U.N. Security Council imposed new sanctions on North Korea at the end of November after Pyongyang carried out its fifth and largest nuclear test so far in September.
A North Korean ICBM, once fully developed, could threaten the continental United States, which is about 9,000 km (5,500 miles) from the North.
ICBMs have a minimum range of about 5,500 km (3,400 miles), but some are designed to travel 10,000 km (6,200 miles) or further.
North Korea worked last year on developing components for an ICBM, making the claim that it was close to a test-launch plausible, international weapons experts said on Monday.
(Reporting by James Pearson and Ben Blanchard; Additional reporting by Jeongeun Lee; Editing by Robert Birsel and Nick Macfie)