Last week, global media observed activity around the site, with reports indicating that North Korean forces were restoring the launch facility, which Pyongyang had previously agreed to dismantle in talks with the U.S.
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Washington and Pyongyang have remained committed to their historic dialogue since the first encounter between Trump and Kim in Singapore last June.
"We've seen a lot in North Korea", he said.
However, he said that if the North went ahead, the USA would be "forced to react" whether it turned out to be a missile test or a satellite launch. We'll take a look.
Asked about the images on Wednesday, Trump said "it's too early to see" if North Korea is breaking a promise by rebuilding the site.More news: Faulty airbag parts prompt Honda to re-recall 1 million cars
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USA -based websites recently released satellite photographs indicating North Korea has restored structures at a long-range rocket launch facility that it dismantled a year ago at the start of diplomacy with the United States.
Bolton said that Trump "is confident in his relations with Kim Jong Un". He said the Hanoi summit showed how "difficult" and "painful" it would be to achieve de-nuclearisation on the Korean Peninsula.
"The technology for making sure you put the satellite into the right orbit is the same technology for making sure the missile is on the right course", Dr Lewis said, noting that previous North Korean space launches used older technology.
Mr Bolton added: "It's possible that North Korea will go back and rethink the position they came in with and come back to talk to the president about the big deal".
Speaking about the reported activities at the North Korean site, President Donald Trump told reporters last week that "I would be very disappointed if that were happening".
The Hanoi summit fell apart due to disputes over how much sanctions relief North Korea should receive in return for limited nuclear disarmament steps.
He also says Trump would "be pretty disappointed if Kim Jong Un went ahead and did something like that" after he vowed not to at a summit in Vietnam. But the meeting collapsed over an impasse over how many weapons sites North Korea would shut down and the extent of economic sanctions relief the USA would offer in return.