Doug Stanglin

USA TODAY

North Korea confirmed Saturday that leader Kim Jong Un was on a train to Vietnam for his second summit with President Donald Trump.

Russia's TASS news agency, quoting a North Korean source, reported earlier that Kim's train was leaving from Pyongyang for the journey across China to Vietnam.

A similar green and yellow train was seen crossing a bridge from North Korea into the Chinese border city of Dandong, according to the Associated Press.

Kim and Trump are set to hold their summit Wednesday and Thursday.

The 2,700-mile trip from the North Korean capital to Hanoi will take more than 48 hours.

Earlier, the Vietnamese foreign ministry tweeted that Kim will make an "official friendly visit" to Vietnam "in the coming days."

Trump said this week that North Korea must do "something that's meaningful" on denuclearization before he would support lifting economic sanctions, a possible point of contention in next week's summit.

“I think they want to do something," Trump told reporters at the White House, though he again tamped down expectations for the summit.

"I don't think this will be the last meeting."

Kim and Trump met last year in Singapore in the first-ever meeting between a North Korean leader and an American president.

At the summit, Kim pledged to eliminate his country's nuclear weapons programs, but some U.S. officials said North Korea has yet to take concrete, verifiable steps to that end. The U.S. is looking for firmer commitments at the Vietnam summit.

North Korea, meanwhile, wants the United States and other countries to start reducing economic sanctions before it makes major changes to its nuclear program.

Contributing: David Jackson in Washington, D.C.