U.S. Secretary of State Mike Pompeo, second from right, greets Kim Yong Chol, second from left, a North Korean senior ruling party official and former intelligence chief, as they arrive for a meeting at the Park Hwa Guest House in Pyongyang, North Korea, Friday, July 6, 2018. Pompeo is on a trip traveling to North Korea, Japan, Vietnam, Abu Dhabi, and Brussels. Also pictured is Andrew Kim, the head of the CIA's Korea Mission Center, right. (AP Photo/Andrew Harnik, Pool)
Andrew Harnik/AP
U.S. Secretary of State Mike Pompeo, second from right, greets Kim Yong Chol, second from left, a North Korean senior ruling party official and former intelligence chief, as they arrive for a meeting at the Park Hwa Guest House in Pyongyang, North Korea, Friday, July 6, 2018. Pompeo is on a trip traveling to North Korea, Japan, Vietnam, Abu Dhabi, and Brussels. Also pictured is Andrew Kim, the head of the CIA's Korea Mission Center, right. (AP Photo/Andrew Harnik, Pool)
Now playing
02:43
Trump touts confidence in Kim Jong Un
CNN
Now playing
02:52
Trump: Kim Jong Un has been open, terrific
Pleiades © CNES 2018, Distribution Airbus DS
Now playing
01:08
New North Korea images spark concern
US Secretary of State Mike Pompeo (3rd L) shakes hands with North Korea's Foreign Minister Ri Yong Ho (3rd R) as they arrive for a group photo at the ASEAN Regional Forum Retreat during the 51st Association of Southeast Asian Nations (ASEAN) Ministerial Meeting (AMM) in Singapore on August 4, 2018. - Leaders, ministers and representatives are meeting in the city-state from August 1 to 4 for the ASEAN Ministerial Meeting (AMM). (Photo by Mohd RASFAN / AFP)        (Photo credit should read MOHD RASFAN/AFP/Getty Images)
MOHD RASFAN/AFP/AFP/Getty Images
US Secretary of State Mike Pompeo (3rd L) shakes hands with North Korea's Foreign Minister Ri Yong Ho (3rd R) as they arrive for a group photo at the ASEAN Regional Forum Retreat during the 51st Association of Southeast Asian Nations (ASEAN) Ministerial Meeting (AMM) in Singapore on August 4, 2018. - Leaders, ministers and representatives are meeting in the city-state from August 1 to 4 for the ASEAN Ministerial Meeting (AMM). (Photo by Mohd RASFAN / AFP) (Photo credit should read MOHD RASFAN/AFP/Getty Images)
Now playing
01:49
Pompeo delivers Trump's letter to N. Korea
TOPSHOT - US President Donald Trump (R) poses with North Korea's leader Kim Jong Un (L) at the start of their historic US-North Korea summit, at the Capella Hotel on Sentosa island in Singapore on June 12, 2018. - Donald Trump and Kim Jong Un have become on June 12 the first sitting US and North Korean leaders to meet, shake hands and negotiate to end a decades-old nuclear stand-off. (Photo by SAUL LOEB / AFP)        (Photo credit should read SAUL LOEB/AFP/Getty Images)
SAUL LOEB/AFP/AFP/Getty Images
TOPSHOT - US President Donald Trump (R) poses with North Korea's leader Kim Jong Un (L) at the start of their historic US-North Korea summit, at the Capella Hotel on Sentosa island in Singapore on June 12, 2018. - Donald Trump and Kim Jong Un have become on June 12 the first sitting US and North Korean leaders to meet, shake hands and negotiate to end a decades-old nuclear stand-off. (Photo by SAUL LOEB / AFP) (Photo credit should read SAUL LOEB/AFP/Getty Images)
Now playing
02:11
UN: N. Korea still pursuing missiles program
TOPSHOT - North Korea's leader Kim Jong Un (L) shakes hands with US President Donald Trump (R) after taking part in a signing ceremony at the end of their historic US-North Korea summit, at the Capella Hotel on Sentosa island in Singapore on June 12, 2018. - Donald Trump and Kim Jong Un became on June 12 the first sitting US and North Korean leaders to meet, shake hands and negotiate to end a decades-old nuclear stand-off. (Photo by Anthony WALLACE / POOL / AFP)        (Photo credit should read ANTHONY WALLACE/AFP/Getty Images)
ANTHONY WALLACE/AFP/AFP/Getty Images
TOPSHOT - North Korea's leader Kim Jong Un (L) shakes hands with US President Donald Trump (R) after taking part in a signing ceremony at the end of their historic US-North Korea summit, at the Capella Hotel on Sentosa island in Singapore on June 12, 2018. - Donald Trump and Kim Jong Un became on June 12 the first sitting US and North Korean leaders to meet, shake hands and negotiate to end a decades-old nuclear stand-off. (Photo by Anthony WALLACE / POOL / AFP) (Photo credit should read ANTHONY WALLACE/AFP/Getty Images)
Now playing
02:25
Pompeo: Kim Jong Un not acting consistently
Airbus Defense and Space
Now playing
01:44
New images show N. Korea dismantling test site
CNN
Now playing
01:32
Clarke: Trump diminishes US role and influence
Now playing
01:16
Source: N. Korea seeking 'bold move' from US
Now playing
02:07
Trump privately expressed N. Korea frustration
Photo Illustration/Getty images
Now playing
02:01
North Korea officials skip meeting with US
SINGAPORE, SINGAPORE - JUNE 12:  In this handout photograph provided by The Strait Times, North Korean leader Kim Jong-un (L) with U.S. President Donald Trump (R) during their historic U.S.-DPRK summit at the Capella Hotel on Sentosa island on June 12, 2018 in Singapore. U.S. President Trump and North Korean leader Kim Jong-un held the historic meeting between leaders of both countries on Tuesday morning in Singapore, carrying hopes to end decades of hostility and the threat of North Korea's nuclear programme. (Photo by Kevin Lim/The Strait Times/Handout/Getty Images)
Kevin Lim/The Strait Times/Handout/Getty Images
SINGAPORE, SINGAPORE - JUNE 12: In this handout photograph provided by The Strait Times, North Korean leader Kim Jong-un (L) with U.S. President Donald Trump (R) during their historic U.S.-DPRK summit at the Capella Hotel on Sentosa island on June 12, 2018 in Singapore. U.S. President Trump and North Korean leader Kim Jong-un held the historic meeting between leaders of both countries on Tuesday morning in Singapore, carrying hopes to end decades of hostility and the threat of North Korea's nuclear programme. (Photo by Kevin Lim/The Strait Times/Handout/Getty Images)
Now playing
01:28
Trump touts North Korea denuclearization
SINGAPORE - JUNE 12: In this handout photo, North Korean leader Kim Jong-un shakes hands with U.S. President Donald Trump during their historic U.S.-DPRK summit at the Capella Hotel on Sentosa island on June 12, 2018 in Singapore. U.S. President Trump and North Korean leader Kim Jong-un held the historic meeting between leaders of both countries on Tuesday morning in Singapore, carrying hopes to end decades of hostility and the threat of North Korea's nuclear program. (Photo by Kevin Lim/THE STRAITS TIMES/Handout/Getty Images)
Handout/Getty Images AsiaPac/Getty Images
SINGAPORE - JUNE 12: In this handout photo, North Korean leader Kim Jong-un shakes hands with U.S. President Donald Trump during their historic U.S.-DPRK summit at the Capella Hotel on Sentosa island on June 12, 2018 in Singapore. U.S. President Trump and North Korean leader Kim Jong-un held the historic meeting between leaders of both countries on Tuesday morning in Singapore, carrying hopes to end decades of hostility and the threat of North Korea's nuclear program. (Photo by Kevin Lim/THE STRAITS TIMES/Handout/Getty Images)
Now playing
01:56
Kim Jong Un snubbed Mike Pompeo, source says
U.S. Secretary of State Mike Pompeo, left, speaks during a meeting with North Korean Director of the United Front Department Kim Yong Chol at the Park Hwa Guest House in Pyongyang, North Korea, Friday, July 6, 2018. Pompeo is on a trip traveling to North Korea, Japan, Vietnam, Abu Dhabi, and Brussels. (AP Photo/Andrew Harnik, Pool)
Andrew Harnik/AP
U.S. Secretary of State Mike Pompeo, left, speaks during a meeting with North Korean Director of the United Front Department Kim Yong Chol at the Park Hwa Guest House in Pyongyang, North Korea, Friday, July 6, 2018. Pompeo is on a trip traveling to North Korea, Japan, Vietnam, Abu Dhabi, and Brussels. (AP Photo/Andrew Harnik, Pool)
Now playing
02:09
N. Korea to Pompeo: You may not have slept well
WASHINGTON, DC - MAY 09:  National Security Adviser John Bolton speaks on a morning television show from the grounds of the White House, on May 9, 2018 in Washington, DC. Yesterday President Donald Trump announced that America was withdrawing from the Iran nuclear deal.  (Photo by Mark Wilson/Getty Images)
Mark Wilson/Getty Images
WASHINGTON, DC - MAY 09: National Security Adviser John Bolton speaks on a morning television show from the grounds of the White House, on May 9, 2018 in Washington, DC. Yesterday President Donald Trump announced that America was withdrawing from the Iran nuclear deal. (Photo by Mark Wilson/Getty Images)
Now playing
01:34
Bolton: US has plan for denuclearizing N. Korea
(CNN) —  

Secretary of State Mike Pompeo said getting North Korea to dismantle its nuclear and missile programs is a “decades long challenge,” as President Donald Trump said Monday he remains confident Kim Jong Un will follow through on his pledges to do so.

Pompeo was speaking to troops during an unannounced stop in Afghanistan, days after North Korea blasted his performance during talks in Pyongyang, accusing the US of “gangster-like” behavior.

“Look, this is a decades long challenge, getting the North Koreans to make a fundamental strategic decision, which is that the nuclear weapons that they possess today frankly present a threat to them and not security,” Pompeo said.

The State Department said the secretary’s mention of ‘decades’ refers to how long the US has been confronted by the threat of a nuclear weapons program in North Korea and not a timeline for resolving the crisis.

The top US diplomat said North Korea has “for decades told their own people that without nuclear weapons their country was at risk of being attacked by the west, by America, by some other country.” The job for the US now, he said, is “to get the entire country to understand that they have that strategically wrong. Chairman Kim told President Trump he understood that. I was there. I saw it.”

Making that happen will take time, Pompeo said. “To think that this would happen in the course of a handful of hours would have been ludicrous, and I’ve been accused of many things, but not that.”

Trump emerged from his Singapore summit with Kim boldly declaring that the US and North Korea had achieved a historic result and that North Korea was “no longer a nuclear threat,” even though North Korea agreed on paper to no concrete actions or specific timeline for denuclearization – merely reiterating previous unfulfilled commitments to peace and denuclearization.

Trump still appears to believe that the document he and Kim signed at the conclusion of their Singapore summit holds more weight than experts believe, referring to it on Monday as a “contract” and reaffirming the importance of his personal interactions with Kim by touting their “handshake.”

“I have confidence that Kim Jong Un will honor the contract we signed &, even more importantly, our handshake,” Trump tweeted on Monday. “We agreed to the denuclearization of North Korea.”

Pompeo on Monday laid out the steps to creating “a peaceful solution,” a painstaking process that will involve “fundamental changes in the relationship between our two countries.”

This will involve bringing North Korea “into the community of nations and then we’ll provide security assurances for their country as well,” Pompeo said, “adequate so that they know their country can stand on its own two feet and not be under threat.”

“If we can figure out how to piece that together, Chairman Kim has made very clear he’s prepared to denuclearize and we’re going to hold him accountable for that commitment,” Pompeo said. There’s many hours left in negotiation.”

01:09 - Source: CNN
Watch Trump salute North Korean general

Trump indirectly referred to the “gangster” comment Monday, pointing a finger at China and accusing North Korea’s powerful neighbor of possibly “exerting negative pressure on a deal” because of ongoing US-China trade disputes.

“Hope not!” Trump tweeted.

Joel Wit, a senior fellow at the Stimson Center and founder of 38 North, a website focused on North Korea analysis, said it wasn’t likely that Pyongyang was acting at China’s behest, as Trump and South Carolina Republican Sen. Lindsey Graham claim.

“The North Korea pronouncement was very typical of their pronouncement. It was not aberration, it was very typical of their foreign ministry statements, so you know, I just think he’s wrong,” Wit said.

North Korea’s “gangster” statement runs counter to Trump administration hopes that Kim is charting a new course for North Korean denuclearization and prompted North Korea experts to warn that Kim was repeating the same tactics his father and grandfather used during previous rounds of similar talks.

Pompeo on Sunday brushed aside the North Korean statements in Tokyo on Sunday, responding: “If those requests were gangster-like, the world is a gangster.”

Clarification: This story has been updated to reflect the State Department’s understanding of Pompeo’s comment that dealing with North Korea’s nuclear program is a “decades long challenge.”