If not, and diplomatic talks fail, the US does have "contingencies" in place, Biegun said.
Trump told reporters Thursday he will wait to see if a border security spending deal can be struck before deciding whether he will use a national emergency declaration to access border wall funding within the Pentagon budget.
"If the USA miscalculates our people's patience, forces something upon us and pursues sanctions and pressure without keeping a promise it made in front of the world, we have no option but to explore a new path in order to protect our sovereignty and achieve peace on the Korean peninsula", stated Kim Jong Un. Biegun said he would push for progress on that again in his upcoming meetings.
North Korea has balked at such a demand, claiming an inventory will give the USA a list of targets to destroy.
The information from Biegun goes further than remarks by Pompeo himself after his trip and beyond any public statement by Pyongyang.More news: Liverpool boss Jurgen Klopp explains Leicester snow controversy
Stephen Biegun also stressed that Washington is embarking on a series of negotiations with Pyongyang ahead of a late February Trump-Kim summit to develop a roadmap for denuclearization.
Responding to questions after his speech, Mr Biegun said it was correct that the U.S. would not lift sanctions until North Korean denuclearisation was complete, but added: "We did not say we will not do anything until you do everything". "They're doing tests and we don't want to be a position where we're behind".
Kim Jong Un has met with Xi four times, and their most recent summit took place in January.
The situation on the Korean Peninsula has reportedly improved since beginning of 2018 during which time North and South Korea concluded important agreements and Kim Jong-un and Donald Trump held a historic summit in Singapore in June past year.
Pyongyang has yet to take concrete steps in that direction, in Washington's view, and the director of USA national intelligence, Mr Dan Coats, told Congress on Tuesday that it was unlikely to give up all of its nuclear weapons and has continued activity inconsistent with pledges to denuclearise.
Preparing the summit, the State Department said Mr Biegun would travel on Sunday to South Korea and also meet his North Korean counterpart.More news: Amazon Revenues Climb 20 Percent to $72.4 Billion
However, he reiterated the USA would not lift sanctions until denuclearisation was complete, and said Washington had "contingencies" in case diplomatic efforts failed again.
Biegun said both he and Trump were convinced it was time to move past 70 years of war and hostility on the Korean Peninsula, but stopped short of suggesting the summit could yield an end-of-war declaration North Korea has been seeking.
"North Korea relationship is best it has ever been with U.S.", Trump tweeted Wednesday.
In a speech at Stanford University Thursday afternoon, Biegun noted that North Korean leader Kim Jong-un had sought unspecified reciprocal measures from the United States in exchange for denuclearization. "Perhaps Intelligence should go back to school", Trump said.More news: Iran face Japan in Asian Cup semifinals