DANDONG, China/SEOUL -- North Korean leader Kim Jong Un left Pyongyang Station on Saturday for Hanoi, the official Korean Central News Agency reported Sunday. His special train will pass through China en route to Vietnam, where he will meet U.S. President Donald Trump for a second time.
He is accompanied by officials including Kim Yong Chol, the chief negotiator and vice chairman of the ruling Workers' Party of Korea's Central Committee, KCNA said.
The leader is expected to arrive in Hanoi on Tuesday, one day before his two-day meeting with Trump begins, even as questions linger over the full scope of the North's nuclear and missile programs.
Kim departed Pyongyang on Saturday evening on an armored train, Russian news agency Tass reported, citing a North Korean diplomatic source. He likely crossed the border into China that night.
Traveling the entire route of well over 4,000 km by train would take nearly three days. The North Korean leader opted against flying for safety reasons, and taking the train through China gives him another opportunity to showcase Pyongyang's warm relationship with Beijing.
Security was tightened in the Chinese border city of Dandong, with hotels in the vicinity barred from accepting guests on Saturday and Sunday.
Kim has visited China twice by air and twice by rail, and he took an Air China plane to his first meeting with Trump in Singapore last June. When Kim's grandfather Kim Il Sung visited Vietnam in 1958, he traveled by train to Beijing before flying the rest of the way.
Vietnam's Foreign Ministry said on Saturday that Kim Jong Un would make an official visit "in the coming days." American and North Korean officials have been holding talks there to lay the groundwork for the summit.
Denuclearization "is the overriding goal" of the summit, a senior Trump administration official told reporters on Thursday. The two sides are working toward a joint statement that cites progress made toward that end, the official said.
But observers are questioning whether the U.S. will stand fast on its demands in the face of the North's reluctance to divulge the full extent of its capabilities, or instead focus on simply confirming the destruction of known facilities.
Since the first Washington-Pyongyang summit, the North has specifically mentioned shutting down or dismantling only the missile base at Tongchang-ri, the nuclear test site at Punggye-ri and the Yongbyon nuclear complex, which make up just a part of its program.
Adam Mount, a senior fellow at the Federation of American Scientists, argues that North Korea plans to refuse inspections and conceal nuclear facilities and weapons.
The Center for Strategic and International Studies, an American think tank, has since November revealed the existence of multiple previously undisclosed North Korean missile bases and estimates that the country has 15 to 20 in operation. These facilities do "not appear to be the subject of denuclearization negotiations," CSIS said.
The U.S. magazine The Diplomat in July revealed details about a covert uranium enrichment site known to U.S. intelligence officials as Kangson. The facility is older than Yongbyon and, by some reports, has double the capacity.
The American approach to denuclearization has already changed, said Joseph Yun, a former U.S. special representative for North Korea policy.
Washington needs a comprehensive declaration of the North's weapons of mass destruction missile programs "before the process of denuclearization can be final," Stephen Biegun, the current envoy to Pyongyang, said last month. This seems to be a step back from previous demands that such a report be provided as a first step.
U.S. intelligence officials sound increasingly skeptical that North Korea will completely scrap its nuclear program, including its weapons. Some observers argue that the destruction of missile bases is just for show, given that the country still has mobile launchers.
If the U.S. prioritizes the destruction of known facilities instead of full disclosure by North Korea, it could end up reward Pyongyang without before reaching the goal of denuclearization.