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

“We will both try to make it a very special moment for World Peace!” Trump said in a tweeted announcement.

The location and date of the summit — the first ever between a sitting US president and a North Korean leader — were revealed hours after three American prisoners were released by North Korea and arrived back in the United States.

Officials said that step removed the last major obstacle to the nuclear-focused summit, providing Trump with tangible evidence that his policy of engagement was reaping rewards.

The small Southeast Asian city state of Singapore has long acted as a bridge between the United States and China.

The Trump-Kim summit has no precedent in US-North Korean relations. No US president has met with his North Korean counterpart while in office.

Despite the optimism of that moment, a deal to limit North Korea's nuclear programme ultimately failed.

A decade on, the nuclear threat with North Korea has only grown, with the country 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.

So far the regime has not indicated it is willing to do that. Hardliners are likely to see possession of a nuke as the only guarantee against US-led efforts to topple the regime.

Pyongyang has yet to indicate its price for any move toward denuclearisation and may yet demand US troops withdraw from South Korea as a quid pro quo.

That complex strategic puzzle will be the focus of the June 12 summit between two relatively new and untested leaders.