A week before a second summit with Democratic People's Republic of Korea (DPRK) leader Kim Jong Un, U.S. President Donald Trump held out the prospect of an easing of tough sanctions on the country, but only if it does "something that's meaningful" on denuclearization.

Speaking to reporters at the White House on Wednesday, Trump also said he expects to meet with Kim again after their February 27-28 summit in Hanoi, the Vietnamese capital.

Trump said he did not think the DPRK was reluctant to denuclearize, in spite of a lack of concrete progress since he and Kim met for a first summit in Singapore in June.

"I don't think they're reluctant; I think they want to do something," he said. "We'll see what happens. The sanctions are on in full. I haven't taken sanctions off, as you know. I'd love to be able to, but in order to do that, we have to do something that's meaningful on the other side."

Trump said he and Kim had "a good relationship" and added: "I wouldn't be surprised to see something work out."

He said he and Kim have made a lot of progress but "that doesn't mean this will be the last meeting."

Trump spoke as his special envoy for the DPRK was due in Hanoi to finalize preparations for the summit. Stephen Biegun is expected to hold talks with his counterpart Kim Hyok Chol, who arrived in Hanoi on Wednesday.

Trump said on Tuesday he wants the DPRK to end its nuclear program "ultimately," but had no pressing schedule for this, provided it stuck to a freeze in nuclear and missile testing in place since 2017.

Sources in Hanoi said earlier that Vietnam was preparing for Kim Jong Un to arrive by train for the summit with Trump.

It could take Kim at least two and a half days to travel the thousands of kilometers through China by train, from the DPRK capital of Pyongyang to Vietnam, meaning he would have to set off later this week in time for his planned February 25 arrival.

Meanwhile, White House Press Secretary Sarah Sanders said in a statement that Trump and Abe in their phone call on Wednesday reaffirmed their commitment to achieving the final, fully verified denuclearization of the DPRK and discussed the upcoming Hanoi summit between Trump and Kim at the end of this month.

Trump and Abe committed to coordinating closely in advance of the U.S.-DPRK talks, according to the statement.

"We firmly and closely coordinated our policies in the run-up to the second U.S.-North Korea summit to resolve nuclear, missile and abduction issues," Abe said after the phone talks with Trump.