* US, N.Korea leaders meet for second summit in Hanoi
* First summit led to only vague agreement on denuclearisation
* Pressure on both sides to agree on concrete steps this time
* Trump touts 'great opportunity' for his friend Kim


US President Donald Trump hailed North Korea's "awesome" potential on Wednesday and said its leader, Kim Jong Un, wanted to do something great, hours before they were due to meet to try to break a stalemate over the North's nuclear weapons.
Despite little progress on his goal of ridding North Korea of its weapons programmes, Trump appeared to be betting on his personal relationship with North Korea's young leader, and the economic incentive after 70 years of hostility between their countries.
"Vietnam is thriving like few places on earth. North Korea would be the same, and very quickly, if it would denuclearize," Trump said on Twitter, the morning after he arrived in the Vietnamese capital of Hanoi for a second summit with Kim.
"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!"
He later said he was looking forward to the talks with Kim and hoped for success.
"He wants to do something great," Trump said.
Trump and Kim will meet at the Metropole hotel at 6:30 p.m. (1130 GMT) for a 20-minute, one-on-one chat followed by a dinner with aides, the White House said.
The elegant interior of the 118-year-old Metropole thronged with security and diplomatic personnel from both sides - some snapping pictures - as hotel staff set up tables in a hotel lounge bar.
On Thursday, the two leaders will hold "a series of back and forth" meetings, the White House said. The venue for those talks has not been announced.
Trump said late last year he and Kim "fell in love", and on the eve of his departure for the second summit said they had developed "a very, very good relationship".
Whether the bonhomie can move them beyond summit pageantry to substantive progress on eliminating Pyongyang's nuclear arsenal that threatens the United States is the question that will dominate the talks in Hanoi.
Trump met Vietnamese President Nguyen Phu Trong at the grand, colonial-era presidential palace in the morning to oversee the formal signing of deals by Vietnamese carriers VietJet and Bamboo Airways with Boeing Co to buy 110 planes worth more than $15 billion.
He later met Prime Minister Nguyen Xuan Phuc for lunch.
PRESSURE
At their historic first summit in Singapore last June, Trump and Kim pledged to work toward denuclearisation and permanent peace on the Korean peninsula. North and South Korea have been technically still at war since their 1950-53 conflict, with the Americans backing the South, ended in a truce, not a treaty.
That first meeting between a sitting US president and a North Korean leader ended with great fanfare but little substance over how to dismantle North Korea's nuclear weapons and ballistic missiles.
This time, both sides are likely to feel pressure to agree on specific measures - what concrete steps North Korea will take to give up the weapons, and what the United States will offer in return.
While the United States is demanding North Korea give up all of its nuclear and missile programmes, the North wants to see the removal of a US nuclear umbrella for South Korea.
US intelligence officials have said there is no sign North Korea will ever give up its entire arsenal of cherished nuclear weapons, which it sees as its guarantee of national security. Analysts say it won't commit to significant disarmament unless punishing US-led economic sanctions are eased.
In the run-up to the summit, Trump has indicated a more flexible stance, saying he was in no rush to secure North Korea's denuclearisation.
He has held out the prospect of easing sanctions if North Korea does something "meaningful".
The two sides have discussed specific and verifiable denuclearisation measures, such as allowing inspectors to observe the dismantlement of North Korea's Yongbyon nuclear reactor, US and South Korean officials say.
US concessions could include opening liaison offices, declaring an end to the technical state of the Korean War or clearing the way for inter-Korean projects.
Any deal will face scrutiny from American lawmakers and other sceptics who doubt North Korea is really willing to give up the weapons, and who worry a compromise could squander US leverage and undermine regional interests.
Trump scoffs at the doubters, citing a freeze in North Korea's nuclear and missile tests since 2017, and saying the United States would have gone to war with North Korea if he had not been president.
"The Democrats should stop talking about what I should do with North Korea and ask themselves instead why they didn’t do "it” during eight years of the Obama Administration?" he said on Twitter.
Whatever the outcome, the summit should boost Kim's bid to end his country's pariah status - despite its dire record on human rights - and cement his place, both on the world stage and at home.
As the third-generation leader of one of the world's most impoverished and isolated nations, Kim will again stand as an equal to the president of the world's most powerful country.
For Trump, a deal that eases the North Korean threat could hand him a big foreign-policy achievement in the midst of domestic troubles.
While he is in Hanoi, his former personal lawyer Michael Cohen is testifying before US congressional committees, with the president's business practices the main focus.
Cohen, in testimony he is due to deliver on Wednesday, refers to a comment Trump made to him about avoiding the US military draft for the Vietnam War on medical grounds: "'You think I'm stupid, I wasn't going to Vietnam'," Cohen cites Trump as saying.
"I find it ironic, President Trump, that you are in Vietnam right now," Cohen said, according to a draft statement seen by Reuters.