The report came as Japan finds itself under pressure to soften its hardline stance against Pyongyang following US President Donald Trump's landmark summit with North Korean leader Kim Jong Un last month. Trump had showered Kim with praises, calling him a "very talented man", and made security concessions in return for very little.
USA intelligence officials believe North Korea has been "deceiving" the US, saying the Hermit Kingdom was bolstering production for nuclear weapons at "multiple secret sites" in the past few months, a report stated.
Asked how quickly he believes North Korea will turn over its arsenal, Bolton told CBS he believes Secretary of State Mike Pompeo will be in discussions with North Koreans in the near future about "really how to dismantle all of their WMD and ballistic missile programs in a year".
The US and North Korea were expected to cooperate for follow-up negotiations at a speedy pace, following the summit, but there has been no visible progress so far.
Pompeo told lawmakers on Wednesday that North Korea remains a nuclear threat, but defended Trump's earlier remarks that North Korea no longer remains a nuclear threat.
Bolton dismissed a question about whether Trump has been more willing to criticise U.S. allies than authoritarian leaders of rival nations, including Putin and North Korea's Kim Jong-un.
Trump is scheduled to meet with Putin on July 16, several days after he stops in Brussels for a North Atlantic Treaty Organisation summit. Some aspects of the new intelligence were reported Friday by NBC News.
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The North Koreans may have made a public show of destroying a main nuclear weapons test site before the summit and halted nuclear and missile tests, but "there's no evidence that they are decreasing stockpiles, or that they have stopped their production", a US official told NBC.
Japanese broadcaster NHK reported that Kim Song Nam is now North Korea's point of contact with China.
U.S. intelligence agencies have for at least a year believed that the number of warheads is about 65, as reported last year by The Washington Post. That site is estimated to have produced fissile material for as many as a couple of dozen warheads.
It also reported Pyongyang has secret production facilities, according to the latest evidence they have.
Officials said that the "assessment concludes that there is more than one secret site" but would Kim admit it?
In recent years, the United States, through imagery and computer hacking, has improved its intelligence collection in North Korea. The Defense Intelligence Agency is at the high end with an estimate of about 50, but all the agencies believe Pyongyang is concealing an unknown number, especially smaller tactical ones, in caves and other underground facilities around the country. The White House did not respond to NBC's request for comment on the story, but per the intelligence assessment, it seems likely that Trump would have been briefed on the nuclear production sites ahead of the Singapore summit.
"What our experts have devised is a program that, with North Korean cooperation, with full disclosure of all of their chemical and biological nuclear programs ballistic missile sites. we would be able to dismantle the overwhelming bulk of their programs within a year", Bolton said.