Even if North Korea is co-operative, the magnitude of dismantling its weapons of mass destruction programs, believed to encompass dozens of sites, will be tough, according to Stanford University academics, including nuclear physicist Siegfried Hecker, a leading expert on the North's nuclear program.
The Pentagon declined to address intelligence reports on North Korea's nuclear capability when asked on Monday, saying only that the U.S. military remains postured to "deal with any and all threats on the peninsula" with the goal of allowing "diplomats the space and the time to hopefully make progress coming out of the summit".
Trump's June nuclear summit with Kim yielded no specifics on how North Korea would achieve denuclearization.
This comes on top of a Washington Post report that USA intelligence believes the North Koreans are planning to hide the number of warheads in their arsenal.
US intelligence is not certain how many nuclear warheads North Korea has.
"It is perfectly rational for North Korea to shift the emphasis to developing solid fuel missiles now that it already has a suite of liquid fuel missiles to deter an attack", he said.
Last week, 38 North, a North Korea monitoring project affiliated with Washington's Stimson Center think-tank, said satellite imagery showed the North had been upgrading its Yongbyon nuclear complex.
Bolton said the United States was going into nuclear negotiations aware of Pyongyang's failure to live up to its promises in the past.More news: Saudi singer celebrates end of driving ban on females with song
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A spokesman for South Korean President Moon Jae-in told reporters it's "inappropriate" to comment on reports suggesting North Korea has not stopped construction at weapons facilities and intelligence matters on the whole.
Bolton said in the interview that if Pyongyang cooperated, the two countries could set out a path to dismantle the programs within a year and put the isolated nation of North Korea on target to receive sanctions relief. Korean language watermark on image as provided by source reads: "KCNA" which is the abbreviation for Korean Central News Agency.
Bolton also said on "Face the Nation" that during the US-North Korea summit in Singapore, Kim was "very emphatic several times" about turning over the arsenal, which was a change from previous regimes.
The Trump administration said the talks made progress but would not elaborate.
Unless Secretary of State Mike Pompeocan pull of a miracle when he travels to North Korea this week, we should prepare for the worst. Collins stressed the need for "verifiable, unimpeded, reliable inspections" of the North's weapons programs.
It said the findings support a new, previously undisclosed Defense Intelligence Agency estimate that North Korea is unlikely to denuclearize.
Trump held a summit with dictator Kim Jong Un last month in Singapore, which yielded a joint statement promising North Korea's denuclearization but lacking firm language on how that goal would be verified.
It remains to be seen how far Kim would go in rolling back his nuclear program, which he may see as a stronger guarantee of his survival than whatever security assurances Washington could provide.