US Secretary of State John Kerry and his South Korean counterpart have said that North Korea will gain nothing by threatening tests of its missile or nuclear programmes.
Mr Kerry said the US and its Asian ally will not accept the North as a nuclear power, adding that its rhetoric is “unacceptable”.
Mr Kerry is making his first-ever visit to Seoul amid strong suspicion that North Korea may soon test a mid-range missile.
South Korean foreign minister Yun Byung-se called Pyongyang’s threats a “grave provocation” to the entire international community.
Mr Kerry is in South Korea at the start of four days of talks in East Asia. He also plans to visit China and Japan.
North Korea often times its provocations to generate maximum attention, and Mr Kerry’s presence in Seoul will provide that. Another key date on the calendar is April 15, the 101st birthday of North Korea’s deceased founder, Kim Il Sung.
Mr Kerry’s trip coincides with a new US intelligence report that suggests North Korea could arm a ballistic missile with a nuclear warhead.
The analysis, disclosed at a congressional hearing in Washington DC, said the US Pentagon’s intelligence wing has “moderate confidence” that North Korea has nuclear weapons capable of delivery by ballistic missiles but that the weapon would be unreliable.
However, the Pentagon said that “it would be inaccurate to suggest that the North Korean regime has fully tested, developed or demonstrated the kinds of nuclear capabilities referenced” at the congressional hearing.
James Clapper, the director of national intelligence, also cast doubt on the claim.
President Barack Obama has urged calm, calling on Pyongyang to end its saber-rattling while sternly warning that he would “take all necessary steps” to protect American citizens.
Mr Kerry’s trip marks his first foray to the Asia-Pacific as America’s top diplomat, as the US turns away from Europe and the Middle East and towards the world’s most populous region and fulcrum of economic growth.
It comes on the heels of months of provocative action and repeated threats of nuclear strikes against the US and South Korea. No one is discounting the danger entirely after tests of a nuclear device and ballistic missile technology in recent months.
North Korea is apparently preparing another missile test in defiance of United Nations resolutions.
The Obama administration believes North Korea is preparing for another missile test, said a senior US State Department official travelling with Mr Kerry. “We will show to our allies that we are prepared and we will defend them,” the official said.
To mitigate the threat, however, Kerry is largely depending on China to pressure North Korea to halt its nuclear and ballistic missile programme although so far is China has had little success.
Officials could not say, however, whether Pyongyang under its enigmatic young leader, Kim Jong Un, was actually listening to anyone at this point.
Kim’s actual control of the country also is unclear, the official added. Now 29 or 30, the product of a Swiss boarding school inherited power from his late father, Kim Jong Il, 16 months ago and has lead his country on an increasingly reckless path of confrontation.