North Korea could dismantle its key nuclear test site as early as Thursday, if weather conditions permit, an official said, according to information from South Korea's media corps.

South Korean reporters on Wednesday joined a small group of foreign media outlets that will cover the dismantling of the Punggye-ri nuclear test site, after Pyongyang ended its days-long refusal to acknowledge their participation.

The foreign journalists invited by North Korea left for the test site in the evening on a special train from the country's eastern coastal city of Wonsan, according to the official China Central Television.

"The special train departed from Wonsan station at 7 p.m. local time," a CCTV journalist reported from inside the train by phone.

A South Korean government transport plane carrying the country's journalists arrived in Wonsan just a couple of hours before their expected departure.

[DigitalGlobe/38 North via Getty/Kyodo]

The foreign journalists are expected to need more than 15 hours of travel time to reach the nuclear facility, which is located in mountainous terrain in the northeast of North Korea.

The facility is where Pyongyang carried out all six of its nuclear weapons tests to date, beginning in 2006, including the most powerful one last September.

The list of the South Korean journalists selected to witness the shutdown was at last accepted by North Korea in the morning, according to Seoul's Unification Ministry.

The approval came a day after a group of around 20 foreign reporters, including some from China and the United States, arrived in Wonsan on a chartered flight.

North Korea has said it will hold a ceremony to mark the closure of the key test site between Wednesday and Friday, depending on weather conditions, and that journalists from China, Russia, the United States, Britain and South Korea will be allowed to conduct on-the-spot coverage of the event.

North Korea remained unresponsive until Tuesday to South Korea's efforts to convey the list through their communication channel at the truce village of Panmunjeom.

Without the required visas, the journalists were unable to board the chartered flight arranged by Pyongyang.

(Foreign journalists gather in Beijin international airport before heading for North Korea)

Despite easing tensions on the Korean Peninsula, North Korea has taken issue with Seoul's military exercises with Washington.

Without providing an explanation, North Korea had declined to accept the list of eight South Koreans -- four each from a news agency and a broadcaster -- since last Friday.

The refusal followed North Korea's abrupt cancellation of a meeting of senior officials of the two countries slated for last week, where they were set to discuss follow-up measures to the historic inter-Korean summit on April 27.

Meanwhile, regarding the summit slated for June 12 between North Korean leader Kim Jong Un and U.S. President Donald Trump, Trump said Tuesday the meeting -- the first ever between a sitting U.S. president and a North Korean leader -- could be called off unless "certain conditions" are met.

"There's a very substantial chance that it won't work out," Trump said just before a meeting with South Korean President Moon Jae In at the White House. "It may not work out for June 12."

Seated with Moon in the Oval Office, Trump noted that preparations for the summit will continue and he believes Kim is "serious" about abandoning his nuclear weapons program.