On Wednesday morning, ahead of his second summit with North Korean leader Kim Jong-un, he said on Twitter: "Vietnam is thriving like few places on earth. North Korea would be the same, and very quickly, if it would denuclearize. The potential is AWESOME, a great opportunity, like almost none other in history, for my friend Kim Jong Un. We will know fairly soon - Very Interesting!"

U.S. President Donald Trump has dangled a big carrot for North Korea to denuclearize.

Trump and Kim will meet on Wednesday and Thursday.

Kim arrived in the Vietnamese capital Tuesday morning in his armored train while Trump landed Tuesday night in his Air Force One.

The former is staying at the Melia Hotel and the latter at the JW Marriott  Hotel.

The two are expected to meet at Hanoi’s French-colonial-era Metropole Hotel at 6:30 p.m. (1130 GMT) Wednesday and have a 20-minute one-on-one conversation before a dinner scheduled to last just over an hour and a half, the White House said.

The two-day summit is expected to discuss ways to improve the bilateral relationship, establishing long-term peace on the Korean Peninsula and returning the remains of U.S. soldiers killed during the Korean War.