CBS News had previously reported Singapore and Mongolia were the top two sites under consideration.
At the same time, Gardner said, Trump's eyes were wide open about the risks of failure and the need to be clear that denuclearization means abandoning nuclear weapons.
Pompeo is himself just back from Pyongyang, after securing the first fruit of the tentative thaw in ties between Washington and Kim's regime - the return of three American detainees.
"We've picked a time". "And I think it'll be very successful".
Singapore is the best alternative option for both nations because it has maintained close diplomatic ties to the USA, and has also established relations with North Korea, with a North Korean Embassy on its soil.
Pompeo urged Pyongyang to take "bold action to quickly denuclearise". Pyongyang has been exceptionally cautious about its public framing of Kim's recent diplomatic moves, which are a major shift from the more aggressive focus on missile launches and nuclear development that drove tensions to a boil past year. For instance, in 2015, Chinese President Xi Jinping chose Singapore for his historic talks with his the then Taiwanese counterpart Ma Ying-jeou.
Fifth, Singapore is the chair of the Association for Southeast Asian Nations or Asean this year and holding a key summit there could send a positive signal to the regional grouping - about possible future engagements - economic, political and military.
Abe praised Kim for his recent "dynamic" moves, citing his two trips to China in a matter of weeks and his deciding to hold talks with Trump. But he says Trump deserves credit for bringing Kim to the negotiating table.
But White House officials opposed the idea as it could put undue emphasis on South Korea.
Trump confirmed the Americans' release on Wednesday morning, saying the group was airborne.
Some 120,000 people are believed to be imprisoned in North Korea without due process, according to the Committee for Human Rights in North Korea (HRNK). "We are very, very happy".
Despite the high probability of a meeting between the USA and North Korean leaders, it is yet unclear whether the sides will be able to reach agreement, the expert noted.
And, more than two decades and multiple provocative weapons tests after the last accord, the threat from Pyongyang has only grown.
The last American to be freed - Otto Warmbier, who was jailed for stealing a hotel sign - was released past year but was fatally ill, and died shortly after returning home. "He, likewise, has been incredibly helpful".
"You remember everybody in the fake news when they said 'he's going to get us into a nuclear war?'" he asked.
"I don't want to offer hypotheticals. I want victory for the world".
U.S. officials said their freedom removed the last major obstacle, providing Trump with tangible evidence that his twin-track policy of engagement and "maximum pressure" was working.
The comments came three days after the USA president announced he would violate the worldwide nuclear deal with Iran which imposed strict curbs on Tehran's nuclear programme in return for sanctions relief.
Mr Pompeo said the U.S. aim was clear - "to ensure that North Korean doesn't possess the capacity to threaten, not only the United States but the world, with nuclear weapons".
Pompeo, who first traveled to North Korea as Central Intelligence Agency chief in early April, was only the second sitting secretary of state to visit the nation with which the U.S.is still technically at war.
During their summit at a border truce village, Moon and Kim vaguely promised to work toward the "complete denuclearization" of the Korean Peninsula, but made no references to verification or timetables.
The Panmunjom Declaration for Peace, Prosperity and Unification was signed by South and North Korean leaders, which laid out a peaceful path forward.
Abe also said worldwide sanctions should remain in place against North Korea and any rewards must wait until Kim fully abandons his nuclear and missile programs. DPRK is the acronym for the Democratic People's Republic of Korea, North Korea's official name.
President Donald Trump, left, with first lady Melania Trump, watch Secretary of State Mike Pompeo, right, embrace former North Korean detainee Tony Kim, with Kim Hak Song, third from left, and Kim Dong Chul, front, May 10, 2018. The two leaders are expected to meet sometime in June. "North Korea summit" and the denuclearization of North Korea.