The looming high-stakes meeting between US President Donald Trump and North Korea's leader Kim Jong-un "will be a huge event, shaking the whole political security dynamics of North-East Asia, not to mention the Korean Peninsula", former UN secretary-general Ban Ki-moon has told the ABC.

Key points: Trump's strong messages were intended to deter North Korea from provocative measures

Trump's strong messages were intended to deter North Korea from provocative measures Mr Ban strongly believes in the power of sports in promoting reconciliation

Mr Ban strongly believes in the power of sports in promoting reconciliation UN can't function properly when there is divisiveness among member states

"I am cautiously optimistic, of course the devil is in the details, so we will have to see, considering that it has been North Korea who has always been abrogating all the agreements and having been the worst known breaker in the world so far," he said.

"We have to be very careful and have a very cool head while the hearts are warm and excited."

Donald Trump (R) has accepted Kim Jong-un's offer of a meeting. ( Reuters: Kyodo/AP: Pablo Martinez Monsivais )

The former United Nations chief — who is also the former foreign minister for South Korea and was a leading presidential candidate before Moon Jae-in became President — currently holds the chair of the International Olympics Commission's ethics commission, which oversaw North Korea's historic attendance at the Winter Olympics last month.

Interestingly, both Mr Moon and Mr Ban have personal ties to the prospect of reunification: Mr Moon's parents were refugees from what is North Korea today, while Mr Ban's own family suffered greatly during the Korean War, an experience that once prompted the former UN boss to declare "reunification is a must".

Speaking to the ABC's The World program, Mr Ban weighed in on Mr Trump's controversial diplomacy, the challenges ahead with Mr Kim, while also reflecting on the ups and downs of his time as head of the United Nations.

Donald Trump's 'fire and fury' rhetoric

"There are some different interpretations and assessments of President Donald Trump's diplomatic style and his rhetoric. I've been trying to interpret it in a more positive way than in dealing with the regime, like North Korea, who has been abrogating all the previous agreements, they have also been threatening the whole world including the United States, that they would strike the heart of US with nuclear weapons. Then in such a case, you may need also some counterbalancing of these kind of unjustified and unacceptable threats. So in that regard, we should try to read the underlying messages of President Trump. I don't believe that he was meaning to engage in any military strategy but the strong messages which he has been sending out was to deter and discourage and stop North Korea from making any provocative measures. In that regard, I think his messages seems to have been heard by North Korea."

Reconciliation through the Winter Olympics

"I'm a strong believer in the power of sports in promoting reconciliation and peaceful co-existence among states. [Sport] has genuine dynamic power, mobilising instantly the sentiment, encouragement and excitement. There is no ideology or no ethnicities or whatever. So that's one vivid, great example which happened during the Winter Olympics Games and Paralympic Games. The composition of a joint women's hockey team as well as some marching together under the one Korean flag, that was most applauded, most moving scene that we have ever seen. This is the power of sports. Then one [of the] most encouraging things which happened is that they were able to make a small room for dialogue between South and North. Of course, President Moon Jae-in of Korea has taken bold initiative of accepting the invitation by North Korean leader. This is what we're now witnessing."

Sorry, this video has expired South Korea's top security adviser makes the announcement at the White House

The effectiveness of the United Nations

"Many people have expressed concerns about the effectiveness of the United Nations, whether it has been doing proper role in addressing [global issues]. But it's simply because of divisiveness among the member states, particularly when the Security Council is seriously divided according to their own national or ideological lines, then there is no way for the United Nations to function properly. This is very sad, and that is why there has been a continuing call among member states that the Security Council should be reformed in a much more representative, democratic and transparent manner."

No one country can solve the world's problems

"What I have been observing particularly during last few years [is] a more nationalistic and isolationist trend among world leaders rather than uniting their strength, uniting their resources when we are facing global threats like climate change and there are many regional conflicts which have global implications. This is caused because of the lack of global vision. There is just no one country, however powerful and resourceful, who can solve all these global issues. We have to unite our resources, we have to unite strength, that's what I have been urging and appealing to world leaders as a secretary-general and now as one of the private citizens. I am only hoping that world leaders will really show their genuine global leadership, genuine global citizenship, that's why I established Ban Ki-moon Centre for Global Citizens [where] I am going to foster global citizenship among young people."