US President Donald Trump and North Korean leader Kim Jong-un on Monday opened their second summit in Hanoi with optimism about eight months after their historic meeting in Singapore.

Trump predicted a "very successful" summit, hoping that this bilateral meeting, which will focus on the issue of denuclearization of North Korea, "is similar or even better than the previous meeting."

"I'm sure we're going to get it this time," said Kim. "I'll do what I can to do it."

Neither Trump nor Kim Jong-un gave any clear indication of what could be announced on the second and final day of the summit in the Vietnamese capital.

Critics of the US president fear he will make many concessions to give the impression of success and divert attention from what is happening in Washington, where his former personal attorney, Michael Cohen, is preparing to testify before a congressional committee.

Hours before the summit, the US president stressed the model of Vietnam, the communist state that adopted capitalism and the front page of confrontation with the United States.

Trump said in a tweet on Twitter: "Vietnam thrives in a way that is unparalleled in only a few places in the world. North Korea can do the same thing very quickly if it decides to disarm. "

"The potential is fantastic. A great opportunity, perhaps unprecedented in history, for my friend Kim Jong-un. We will know very soon. It's very interesting! "

Trump often uses his words to write a few words to emphasize their meaning.

During his meetings with the Vietnamese authorities, Trump also met with President Nguyen Bo Trung, also head of the Communist Party, for "extraordinary" economic progress in Vietnam.

A series of contracts were signed with US companies with a total value of $ 21 billion, according to the White House.