US President Donald Trump on Saturday invited North Korea's Kim Jong-un to shake hands during a visit by Trump to the demilitarised zone with South Korea.

Juncker described the pact with the bloc made up of Argentina, Brazil and Uruguay as "an historic moment" that came 20 years after talks were launched.

And, for the flamboyant, rumpled, ambitious former London mayor Boris Johnson, there's been some tripping up already.

Carter's comments came during a panel discussion at a retreat for donors to the Carter Centre, an organisation he founded in 1982 that has been at the forefront of election monitoring efforts around the globe for decades.

Australian nurse Kirsty Boden "paid the ultimate price", one of London's top police officers said as the inquest drew to a close.