Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

PALM BEACH, Fla. — The Trump administration has made some headway on one of its biggest challenges ahead of President Donald Trump’s meeting with North Korean leader Kim Jong Un later this spring: finding a suitable location for the summit.

A senior U.S. official told NBC News on Wednesday that a number of locations had already been ruled out, including North Korea’s capital, Pyongyang, as well as Beijing and Mongolia, all of which raise security concerns. U.S. officials are instead pushing for a more neutral location, preferably in Europe, with Switzerland among the top choices, the official said.

Bloomberg News reported Wednesday that in addition to Pyongyang and Beijing, Panmunjom — the site of the 1953 signing of the Korean War armistice — had also been ruled out, and that Sweden was another neutral location currently under consideration.

Trump said on Tuesday that his administration was exploring five locations ahead of the proposed summit, which is on track to take place in late May or early June.

The president, a foreign policy novice, has taken an unconventional path to reaching the point of direct talks with North Korea.

U.S. diplomatic efforts waned last year after the death of Otto Warmbier, an imprisoned American college student who was in a coma when U.S. diplomats secured his release from North Korean captivity. Trump later launched a war of words with the North Korean leader, warning that Kim's nuclear tests would be met with “fire and fury” and dubbing him “little rocket man.”

Today, however, Trump's tone is markedly different — due in part to a push toward warmer ties by South Korea's president, Moon Jae-in.

Trump said Wednesday that CIA Director Mike Pompeo's secret meeting with North Korean leader Kim Jong Un over Easter weekend had gone "very smoothly" — helping pave the way for an extraordinary planned summit between the leaders of both nations.

Trump, at his Florida beach resort this week for meetings with Japanese Prime Minister Shinzo Abe, highlighted the progress.

"Mike Pompeo met with Kim Jong Un in North Korea last week," Trump tweeted early Wednesday. "Meeting went very smoothly and a good relationship was formed. Details of Summit are being worked out now. Denuclearization will be a great thing for World, but also for North Korea!"

The top-secret meeting, which was first reported by The Washington Post, came soon after Pompeo was nominated to be Trump's next secretary of state. He has yet to be confirmed by the Senate.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

Trump last month accepted an invitation from Kim, delivered through a visiting South Korea delegation, to meet.

No U.S. leader has ever visited North Korea while serving in the Oval Office. Former Presidents Jimmy Carter and Bill Clinton traveled to the country on peacekeeping missions, but both Democrats had been out of the White House for years before making their trips.

Much of Trump's meetings this week with Abe have centered on regional security and his plans to meet with Kim.

Sitting alongside Abe at his Mar-a-Lago resort here, Trump said Tuesday that U.S. officials had been holding direct talks with the North Korean government at "extremely high levels" ahead of his planned meeting with Kim. He did not elaborate at that time on who was taking part in the meetings or whether the meetings included Kim himself.

Trump's confirmation that the two governments were speaking directly revealed some of the most sustained communication between the two nations in over half a century.

"We have had direct talks at very high levels, extremely high levels with North Korea," Trump told reporters. "And I really believe there is a lot of good will, lot of good things are happening."

It was previously thought that Kim would never agree to leave North Korea given his lack of diplomatic experience and comfort level at home. Other possible locations have presented significant security concerns.

Late last month, Kim, 34, stunned regional officials and experts alike when he journeyed by train for what amounted to a secret trip to neighboring China. His meetings with Chinese President Xi Jinping marked his first trip outside North Korea since taking power in 2011, and his first meeting with another head of state.

Earlier this year, South Korea made some breakthroughs with its warring neighbor after a series of meetings and discussions that resulted in North Korea sending athletes to compete in the Winter Olympics in South Korea. Athletes from the two countries entered the Olympic arena in Pyeongchang under a unified flag, signaling the potential for warmer ties.

South Korea's national security adviser, Chung Eui-yong — who communicated Kim's interest in meeting Trump during a visit to Washington last month — said Wednesday that it will consider negotiating an end to the decades-old Korean hostilities if North Korea commits to denuclearization.

At a joint news conference with Abe on Wednesday at Mar-a-Lago, the president reassured the prime minister that the U.S. would work hard toward denuclearization and to improve diplomacy with North Korea during the upcoming summit.

"We hope to see that day when the whole Korean Peninsula can live together in safety and prosperity," he said.

Abe said Trump has promised to raise the issue of Japanese citizens being abducted by North Korea over the years.

Trump also pledged to step away from the talks if he believes hat they are unsuccessful.

"If we don't think it's going to be successful were not going to have it," he said. "If the meeting, when I'm there, is not fruitful I will respectfully leave the meeting."

No peace treaty has been signed to replace the 1953 armistice that ended the Korean War. The increasing isolation of North Korea over the decades, plus its pursuit of uranium enrichment, has been a great source of concern for countries in the region, including Japan.

Trump said Tuesday that the two Koreas "have my blessing" to end their hostilities.

Pompeo, a hawkish conservative from Kansas who was elected to the House in the 2010 Tea Party wave, said during his confirmation hearing last week that "no one is under any illusions" that the planned summit between Trump and Kim will achieve a comprehensive agreement on the denuclearization of the Korean Peninsula.

During his hearing before the Senate Foreign Relations Committee, Pompeo warned that the U.S. and other countries have rushed to ease sanctions too quickly in past negotiations with Pyongyang and urged vigilance.

"It is the intention of the president and the administration not to do that this time" and to ensure that "before we provide rewards, we get the outcome permanently, irreversibly, that it is that we hope to achieve," Pompeo said.

"It is a tall order, but I am hopeful that President Trump can achieve that through sound diplomacy."

Speaking at the Aspen Security Forum in July 2017, Pompeo said the most dangerous thing about North Korea's nuclear program "is the character who holds the control over them today."

"The North Korean people I'm sure are lovely people and would love to see him go," he added.