The US will have to assure North Korea it won't seek to undermine its leader Kim Jong-un, Secretary of State Mike Pompeo has implied.

That comes after years of slamming him as a dictator and squeezing his country with sanctions.

With less than a month left before the hugely-anticipated talks between US President Donald Trump and North Korea's leader Kim Jong-un in Singapore, the US top diplomat has indicated that any deal paving the way for a nuclear-free Korean peninsula will have to include certain US safeguards allowing Kim to stay in power.

"We will have to provide security assurances to be sure. This has been the trade-off that has been pending for 25 years," Pompeo told 'Fox News Sunday.' Pompeo was speaking to Fox's Chris Wallace just a few days after he returned to the US from his second meeting with Kim, during which they were supposed to thrash out the details of the Trump-Kim summit on June, 12.

The upcoming talks are being hailed as a monumental personal success by Donald Trump, who, just months ago, berated Kim as a "mad man" and as a "rocket man on a suicide mission," threatened him with "fire and fury" and boasted about having a bigger nuclear button. Now, the Trump administration is using the negotiations as a way of saying it's better than the previous ones.

"No president has ever put America in a position where the North Korean leadership thought that this was truly possible that the Americans would actually do this, would lead to the place where America was no longer held at risk by the North Korean regime," Pompeo said.

As for Kim being a "dictator" and "oppressor" with a poor human rights record – apparently, the safety of the US eclipses that.

"Look, we'll have to see how the negotiations proceed. But make no mistake about it: America's interest here is preventing the risk that North Korea will launch a nuclear weapon into L.A. or Denver or to the very place we are sitting here this morning, Chris," Pompeo said.

If the negotiation proves to be a success, North Korea can see private American companies flooding its market, helping to develop its power grid and providing food supplies "so they [North Koreans] can eat meat and have healthy lives." However, he dismissed the possibility that the US taxpayers' money could be involved in the program.

Speaking about the impression the North Korean strongman made on him during their meetings, Pompeo described Kim as always up to date with the agenda and an apt negotiator.

"The conversations are professional. He knows -- he knows his brief, he knows what he is trying to achieve for the North Korean people," Pompeo said, noting that Kim is also keeping tabs on the Western media and "will probably watch the show at some point."

Hinting that the times when a full-blown war of words was raging between Trump and Kim are long forgotten, Pompeo said that neither he nor Kim touched on the "little rocket man" remark by Trump or any other less-than-graceful characteristics given to Kim by the US leader before.

The tone of Trump's rhetoric towards Kim has shifted dramatically over the past several months. Following the landmark summit between Kim and South Korean President Moon Jae-in in late April, Trump has heaped praise on the North Korea leader, raising some eyebrows.

During a meeting with French President Emmanuel Macron last month, Trump called Kim "very open and very honorable."

Following North Korea's pledge to dismantle its nuclear test site and allow foreign journalists, including ones from the US, to oversee the process, Trump thanked him for what he called "a very smart and gracious gesture."