"Time is running out as North Korea is nearing the final stages of the completion of its nuclear development as it claims", the nuclear envoy stressed, adding that he will work toward producing "tangible" progress on the North Korean nuclear weapons front within his term.
"Kim Jong Un would have to accept considerable risk of failure - or worse, a missile carrying a nuclear warhead could crash into Japan - if he elects to use the Hwasong-12 or -14", Elleman said.
On September 15, North Korea launched a medium-range ballistic missile over Japanese territory - several days after the adoption of UN Security Council Resolution 2375.
Jong-un said that will consider his response being the "highest level of hard-line countermeasure".
For reference, the US agency recorded a 6.3 magnitude quake after North Korea's hydrogen bomb test on September 3, its sixth of a nuclear weapon.
A small quake that hit North Korea Saturday near the country's nuclear test site was likely a natural tremor and not a nuclear explosion, neighboring countries said. North Korea will be feeling the pain of new United Nations' sanctions targeting some of its biggest remaining foreign revenue streams, like textiles, joint ventures and remittances from its legion of workers overseas.
If the United States does not ease up, he said, "we could drop into a very unpredictable nosedive and tens if not hundreds of thousands of innocent citizens of South Korea but also North Korea, of course, and Japan will suffer - and Russian Federation and China are nearby".
Such a test with a live warhead would tell North Korea's engineers whether their bomb design can survive the rigours of flight and re-entry into the Earth's atmosphere, says Michael Elleman, a missile defence expert at the International Institute for Strategic Studies.
Xinhau, China's official news agency, said the country's seismic service registered a 3.4 magnitude event that it originally viewed as "likely caused" by an "explosion".
The quake could be the result of a cave in following the test earlier this month.
"This mission is a demonstration of USA resolve and a clear message that the president has many military options to defeat any threat", Pentagon spokeswoman Dana White said.
China announced Saturday that it will limit oil exports to North Korea under United Nations sanctions over its nuclear and missile development, further reducing support from Pyongyang's last major trading partner, energy supplier and diplomatic ally.
Spiking nuclear tensions between the United States and North Korea showed little sign of abating Sunday as Russian Federation warned of a "very unpredictable nosedive" if Washington does not ease up on its fiery war of words with Pyongyang.
Trump used his maiden speech at the United Nations General Assembly on Tuesday to warn that Washington would "totally destroy" the North if America or its allies were threatened.
"If traders were hoping for a strong US dollar rebound in the wake of this week's Fed meeting, the initial response was certainly encouraging (but) beyond that the response has been underwhelming", said CMC Markets analyst Michael Hewson.