"The Kim Jong-un regime has achieved alarming success in its quest to demonstrate the capability to threaten the US homeland with nuclear-armed ICBMs, believing such weapons are necessary to deter USA military action and ensure his regime's survival", the four-star general said in a statement Tuesday submitted to the Senate Armed Services Committee. "If it wants to sleep in peace for (the) coming four years, it had better refrain from causing a stink at its first step".
The two countries remain in a lengthy dispute over North Korea's nuclear and ballistic missile programmes.
The news came as US Secretary of State Antony Blinken and Defense Secretary Lloyd Austin departed for a four-day trip to Japan and South Korea - after which Austin will continue on to India and Blinken will stop in Anchorage, Alaska, where he and US national security adviser Jake Sullivan will meet with Chinese representatives on Thursday.
He noted that Kim's regime also has taken on an increasingly "bellicose" stance toward the United States.
North Korean leader Kim Jong-un's powerful younger sister warned that Pyongyang could scrap the inter-Korean military agreement as she lambasted the annual joint military drills between Seoul and Washington. The drills were scaled down due to the coronavirus risk and in a bid to keep diplomatic channels open.
Shortly before Biden's January inauguration, leader Kim decried the U.S. as his country's "foremost principal enemy" and Pyongyang unveiled a new submarine-launched ballistic missile at a military parade.
Kim's statement, as colourful as it is, is generally consistent with past North Korean statements expressing frustrations at disparities between words and actions, said Jenny Town, director of 38 North, a US-based website that tracks North Korea.
South Korea's defense ministry has urged North Korea to take a flexible stance and resume talks in order to establish permanent peace on the Korean peninsula.
"The North Korean regime has also indicated that it is no longer bound by the unilateral nuclear and ICBM testing moratorium announced in 2018, suggesting that Kim Jong-un may begin flight testing an improved ICBM design in the near future", he said.
- NY channel - Austin and Blinken arrived in Tokyo on Monday and held talks Tuesday that focussed on China but also addressed the new administration's review of United States policy towards Pyongyang.
Seoul's military addressed the North's statement.
North Korean state media has yet to acknowledge Joe Biden is now the American President, having been inaugurated in January.
Seoul and Washington are treaty allies, with the U.S. stationing around 28,500 troops in the South to defend it against its neighbour, and they began computer-simulated joint military exercises last week.
Kim Yo Jong continued this trend, with a large chunk of her statement devoted to slamming South Korea over the exercises.
"War rehearsals can not coexist with dialogue, hostility can not coexist with cooperation", she said.
"We [agreed to] oppose China's unilateral bid to change the status quo, including in the East China Sea and South China Sea, and shared concerns about China's coast guard laws", said Motegi.
Despite Pyongyang's repeated criticism and the blowing up past year of an inter-Korean office, South Korean President Moon Jae-in has staked much of his legacy on engagement that resulted in several meetings with the North Korean leader.
Kim Yo Jong is a trusted adviser to her brother and was a key voice when inter-Korean tensions mounted past year, culminating in the North blowing up a liaison office on its side of the border.
Leif-Eric Easley, an associate professor of global studies at Ewha Womans University in Seoul, said Kim Yo Jong's statement "reeks of hypocrisy", coming after North Korea had conducted its own winter military drills.