When US President Donald Trump and North Korea's Kim Jong-un meet in Hanoi on Wednesday, they will do so with great expectations but much less ability to leave like last time, without concrete evidence that Pyongyang intends to give up its nuclear weapons.
The inaugural summit between the leaders in Singapore last June was hailed by the White House as a sign that the communist state was committed to surrendering its atomic arsenal. Within weeks, officials from Mr Kim's camp were saying the opposite. It is a sign of the higher stakes involved this week that Mr Trump has in recent days declared that he is "in no rush" to see the North denuclearise.
The US president's singular outlook that only he can reach a deal may also have limited the role of US diplomats led by Stephen Biegun, special representative for North Korea, who arrived in Vietnam last week. While they would normally try and agree with their counterparts on what is achievable in Hanoi, Mr Trump's speculative comments may have led the North to think the president is the only person worth talking to. The goals of the second summit remain undefined.
“Clearly, the administration has been deflating expectations,” said Robert Einhorn, former special adviser for non-proliferation and arms control at the State Department.
“The gaps between the two countries remain quite large. It would be far too ambitious to expect denuclearisation. Some ad hoc concessions are more likely.”
Mr Trump has talked up how the North's economy would benefit under a deal. Mr Kim has been guarded, limiting his political exposure to state television and the populist views of him travelling to Vietnam over three days in a train whose maximum speed is 60 kilometres per hour.
A symbolic measure of political progress could be a formal end to the Korean War, a step hinted at by South Korea on Monday. Although fighting ended in 1953, the warring parties only signed an armistice. North and South Korea continue to have troops and weapons at the border.
There could also be an agreement to set up political offices in Washington and Pyongyang. The question of sanctions relief may also arise. While the State Department insists that such measures can only be rescinded when North Korea denuclearises, the North's leader will be loath to allow a return of international inspectors to nuclear sites such as Yongbyon unless he has gained economically.
Although the relationship between Mr Trump and Mr Kim has been the focus ahead of this week's nuclear diplomacy, Pyongyang's neighbours stand to be most affected.
Japan wants complete denuclearisation, given the military threat that North Korea has displayed by firing missiles over the former's territory. The last such incident occurred in August 2017, an achievement Mr Trump talks up as a diplomatic success, despite the North's suspension of such aggression preceding the Singapore summit in June 2018.
Of other regional powers who stand to gain, China, the North's main economic and political partner, would welcome a reduction in the chances of a military confrontation. And Russia would be pleased by even a partial exit of American troops from South Korea which could become part of a new deal between Washington and Pyongyang. Such a step would upset Japan and South Korea, which has re-engaged in inter-Korean relations and backed Mr Trump despite being under threat of a nuclear attack from its neighbour.
“The Republic of Korea voices its support for the goal of denuclearisation but, at this stage at least, would welcome a more realistic goal,” said Mr Einhorn, currently a senior fellow on the arms control and non-proliferation initiative at the Brookings think tank in Washington.
The culmination of the Singapore summit was a joint statement in which the US “committed to give security guarantees” to the North in exchange for Mr Kim “reaffirming his firm and unwavering commitment to complete denuclearisation of the Korean peninsula”.
The latter undertaking looks doubtful. The International Atomic Energy Agency has since said the North is continuing to develop nuclear weapons, as does the CIA.
For all the warm words between Mr Trump and Mr Kim, the diplomatic road has not been invariably smooth either. In August, the White House called off US Secretary of State Mike Pompeo's trip to Pyongyang, reportedly because the North was angry about the lack of progress on a formal end to the Korean War. On Sunday, Mr Pompeo, who has accompanied Mr Trump to Vietnam, was more insistent than the president in saying that denuclearisation remains an American demand.
As such, a declaration that the Korean War has ended could give both the US and North Korea a tangible benefit from the summit and insulate them from claims that the meeting is all for show.
But Christopher Hill, who as US assistant secretary of state for East Asian and Pacific affairs in 2005 led the six-party talks aimed at resolving the North Korean nuclear crisis, said he would be worried if Mr Trump made concessions that involved any pullout of American forces from the South.
Although administration officials said such a change is not on the agenda in Hanoi, Mr Trump undercut the State Department and the Pentagon by announcing a suspension of US-South Korea military exercises during the Singapore talks.
“My worst fear is that in the context of wanting to pull US troops out of Afghanistan and Syria he brings the issue of reducing troops in South Korea into the mix,” Mr Hill, now an academic at the University of Denver, said of Mr Trump.
“One, I don't think the president's going to get complete denuclearisation. And two, I think it's a terrible signal that somehow we would bargain away our very good relationship with South Korea.
“We have bled for each other. South Koreans were with us as far back as Vietnam. People forget about that and I just worry that what we have done over decades could go away because someone says: 'you guys are thinking in some old way'.”
The ceremonial guards and flag-waving crowds that greeted Mr Kim in Vietnam, a communist state that became one of Asia's hottest economies at the turn of the millennium, would appear to feed into Mr Trump's strategy of bringing North Korea in from the cold. But it should not distract him from the key issue of the summit, said Mr Hill who saw Mr Kim's father and predecessor Kim Jong-il agree a deal only to abandon it later.
“North Korea needs to understand that we will not accept nuclear weapons. We've got to have steady, mature but tough leadership on this point,” he added.