U.S. President Donald Trump confirmed Wednesday that CIA chief Mike Pompeo had held clandestine talks with North Korea’s Kim Jong Un, as the two nations move closer to a landmark summit that would see their sitting leaders meet for first time ever.

The meeting came amid a flurry of diplomatic activity involving the U.S., Japan, China and the two Koreas, including news that Seoul was examining the prospect of replacing the armistice that ended fighting in the Korean War with a peace regime.

The seemingly daily onslaught of developments on the Korean Peninsula have raised hopes of a breakthrough in persuading Pyongyang to rein in its nuclear and missile programs at the Kim-Trump summit due to be held by June and before that at a meeting between Kim and South Korean President Moon Jae-in on April 27.

But the latest shocking development came with reports that Pompeo had held a face-to-face meeting with North’s young leader earlier this month.

“Mike Pompeo met with Kim Jong Un in North Korea last week. Meeting went very smoothly and a good relationship was formed. Details of Summit are being worked out now,” Trump tweeted.

“Denuclearization will be a great thing for World, but also for North Korea!” he added.

Kim’s meeting next week with Moon is expected to focus on the denuclearization issue while also discussing a possible peace declaration.

Trump said earlier during a bilateral meeting with Prime Minister Shinzo Abe that the Kim-Moon summit could, with his “blessing,” explore a peace treaty to formally end the conflict.

“We are looking at the possibility of replacing the armistice regime on the Korean Peninsula with a peace regime,” a senior official with South Korea’s presidential Blue House was quoted as saying Wednesday.

“But this is not something we can do by ourselves. It needs close discussions with relevant parties, including North Korea.”

South Korea and a U.S.-led U.N. force are technically still at war with North Korea after the Korean War ended with an armistice, not a peace treaty. The U.S.-led United Nations Command, Chinese forces and North Korea signed the 1953 truce, to which South Korea is not a party.

The April 27 North-South meeting will be just the third summit between leaders of the rival Koreas since the armistice was signed 65 years ago.

Key moments, including Kim and Moon’s first handshake, will be televised live, both sides agreed at working-level talks Wednesday, the Blue House said.

While Trump and Kim have not spoken directly, according to the White House, the U.S. president revealed Tuesday that there had been contact at “very high levels” to prepare for the historic meeting — an apparent reference to Pompeo’s secret visit.

Pompeo, who earlier this year expressed a desire to “separate” North Korea from its regime — an apparent allusion to regime change — told U.S. lawmakers considering his nomination as secretary of state last week that there was more room for diplomacy before considering military action.

Trump, meanwhile, said that “five locations” were being considered for the Kim summit.

“That will be taking place probably in early June or before that assuming things go well. It’s possible things won’t go well and we won’t have the meetings and we’ll just continue to go on this very strong path we have taken.”

Under the Trump administration-led “maximum pressure” campaign, Pyongyang has been slapped with some of the toughest international and unilateral sanctions it has ever faced.

Those sanctions came after months of soaring tensions as the North conducted its most powerful nuclear test and launched more than 20 missiles — including two intermediate-range weapons that flew over Japan and another long-range missile that experts say puts the whole of the United States in striking distance. With the test of that long-range missile in November, the North said it had “realized the great historic cause of completing the state nuclear force.”

Media reports quoting U.S. officials have said that no decision has yet been made on a meeting venue, though Bloomberg News reported Wednesday that locations being discussed include Geneva and venues in Asia and Southeast Asia, it said, quoting a person familiar with the talks.

The source said the U.S. wasn’t considering Beijing, Pyongyang, Seoul or Panmunjom, the site of the Korean armistice signing in 1953.

The sudden talk of rapprochement on the Korean Peninsula has prompted a spate of meetings between leaders and officials from nations with vested interests in the nuclear issue.

Last month Kim made a surprise visit to Beijing to meet President Xi Jinping in what was believed to be the North Korean leader’s first trip outside his isolated nation’s borders since he succeeded his father in 2011.

Top Chinese officials have since traveled to Pyongyang amid mounting speculation Xi might make a reciprocal visit, including a report by CNN on Wednesday that said he is preparing to visit Pyongyang.

It would be the Chinese leader’s first official visit to North Korea since he came to power as head of the Chinese Communist Party in November 2012.

Citing an unidentified official with knowledge of the discussions, the report said the visit will happen “soon,” possibly after the Trump-Kim summit.