US President Donald Trump on Thursday revealed his historic summit with North Korean leader Kim Jong Un will take place in Singapore on June 12.

The location and date of the landmark meeting — the first ever between a sitting US president and a North Korean leader — were announced by presidential tweet just hours after North Korea released three American prisoners.

US officials said their freedom removed the last major obstacle, providing Trump with tangible evidence that his twin-track policy of engagement and “maximum pressure” was working.

“We will both try to make it a very special moment for World Peace!” Trump wrote.

Technically the United States and North Korea are still at war — a stop-gap armistice ended the brutal three-year war between the two countries in 1953 and around 30,000 US troops remain in neighbouring South Korea.

Neutral Singapore has long acted as a bridge between the United States and China, with successive prime ministers offering Oval Office occupants cherished geopolitical counsel.

When Trump and Kim sit down in the sweltering Southeast Asian city-state, the two relatively new and untested leaders face a nuclear puzzle that has eluded seasoned diplomats for decades.

A series of US administrations have sent envoys, both official and unofficial, to Pyongyang in the hope of stopping North Korea’s provocative nuclear weapons program.

Former presidents Bill Clinton and Jimmy Carter visited after leaving office, non-proliferation talks have repeatedly taken place and a deal was even signed in 1994.

But despite the optimism of that moment, all efforts to limit North Korea’s nuclear program have, to date, failed. And more than two decades and multiple provocative weapons tests after the last accord, the threat from North Korea has only grown.

The country is now believed to be on the cusp of developing an intercontinental ballistic missile that could deliver a nuclear warhead to the continental United States.

Trump has vowed that he will not let that happen and has demanded that North Korea give up its nukes.

– ‘Cautious optimism’ –

So far the North Korean regime has made vague pledges to “denuclearize” but not spelt out what that means, when it would happen or how it would be implemented.

In North Korea’s bombastic rhetoric, “denuclearization” has, for years, been a by-word for US troop withdrawals from South Korea and an excuse for stalling.

The regime’s hardliners are believed to see possession of nuclear weapons as the only guarantee against US-led efforts to topple the regime.

But Trump’s high profile meeting offers a glimmer of hope of a breakthrough, according to Republican Senator Cory Gardner, who discussed preparations for the summit with Trump at the White House on Wednesday.

“This is a moment for cautious optimism,” he told AFP. “The president understands that there is a historic opportunity to achieve what the world has been unable to achieve for decades.”

At the same time, Gardner said, Trump’s eyes were wide open about the risks of failure and the need to be clear that denuclearization means abandoning nuclear weapons.

“As of last night there was no nuance in terms of denuclearization,” he said.

But before any technical talk about reprocessed fuel rods, separated plutonium or spent fuel removal, Trump will want to answer one basic question — whether North Korea wants to change.

“This is the key test,” said Gardner. “I think that if Kim Jong Un wants to find relief from ‘maximum pressure’ and be welcomed back to the table of recognized global leadership, it’s the only path he has.”

Since the foundation of North Korea in 1948, the country has endured war and struggled to balance Soviet and Chinese rivalries.

Decades of financial stagnation, international sanctions, mass starvation and industrial scale human rights abuses followed.

“The road we have been down is well travelled and it’s never ended well. So I hope this time is different,” said Gardner.