"One of my worries is that we come out of this Singapore summit with something that looks remarkably like the Six Party Talks or anything that the president has previously criticised but it is hyped as something that's historic and new and groundbreaking", he added.
Kim Jong-un's bodyguards are some of the fittest in the business.
"There is no chance to make North Korean leaders ... surrender their nuclear weapons", Andrei Lankov, a Korea expert at Seoul's Kookmin University, wrote recently on a Washington-based Asia newsletter.
"We will continue to work with our worldwide partners to strictly enforce existing sanctions until such time as North Korea turns its commitments into concrete steps towards denuclearisation".
Trump is expected to offer to lift economic sanctions on North Korea and provide other forms of economic assistance if it agrees to give up its nuclear weapons programs.
It was a far cry from past year when Trump threatened North Korea with "fire and fury" and mocked Kim as "little rocket man", and Kim denounced the U.S. president as the "mentally deranged USA dotard". The North Korean leader met with Singapore Prime Minister Lee Hsien Loong ahead of a historic summit with President Donald Trump on June 12.
Foreign Ministry spokesman Bahram Ghasemi said on Monday that North Korea should approach this week's summit with Mr Trump with "awareness".
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But a government official said they had just agreed to open talks on the basis of the rebel amendment. She insisted: "We must think about the message Parliament will send to the European Union this week".
Mr Pompeo added that the USA was prepared to take action to provide North Korea with "sufficient certainty" that denuclearisation "is not something that ends badly for them".
He would not say whether that included the possibility of withdrawing USA troops from the Korean Peninsula, but said the context of the discussions was "radically different than ever before".
Trump arrived in Singapore on Sunday after a blow-up over trade with other members of the Group of Seven major industrialised nations in Canada.
The public will quickly find out how Trump viewed the summit.
Later, Mr Kim left his luxurious hotel for a late-night city tour hours ahead of the summit. Instead of simply fixing the remaining 5 percent of an agreement, the two leaders are expected to address almost 95 percent of the agenda on their own.
Iran says North Korea should be wary of negotiating with President Donald Trump following his withdrawal from the landmark 2015 nuclear agreement.
The summit capped a dizzying few days of foreign policy activity for Trump, who shocked US allies over the weekend by using a meeting in Canada of the Group of Seven industrialized economies to alienate America's closest friends in the West. Lashing out over trade practices, Trump lobbed insults at his G-7 host, Canadian Prime Minister Justin Trudeau.
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He made his debut in the Argentinian league in 2007 and officiated his first worldwide match in 2010. Reuters contributed reporting to this article.
Asked whether he would invite Kim to the White House, Trump said: "Absolutely, I will".
Pyongyang has said it is willing to deal away its entire nuclear arsenal if the United States provides it with reliable security assurances and other benefits.
"This is not the fault of either Trump or Kim, but rather a reflection that intractable, decades-long strategic challenges rarely-if ever-get resolved in single encounters", Haas writes.
Sung Kim has taken the lead on policy negotiations with North Korea.
But even before then, Trump and Kim could emerge from their meetings on Tuesday declaring a second day of meetings.
Pyongyang's definition of denuclearization is much more opaque, but is believed to be much broader in scope and possibly include things like U.S. nuclear-capability assets in the region, Washington's large troop presence on South Korea or its inclusion of Seoul in its "nuclear umbrella".
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To survive the great unbundling, AT&T needs a content package strong enough to gain it a share of the "over-the-top" media market. Like Disney, Comcast is willing to divest Fox's regional sports networks if regulators demand it, according to company filings .