Donald Trump tore up a G7 agreement and lashed out at his allies as part of a demonstration of strength as he flew into Singapore ahead of Tuesday's crunch talks with Kim Jong-un, according to a senior White House adviser.

The president's blistering attack on his Canadian counterpart - which he continued on Monday in Asia - was part of a ploy to offer no hint of weakness as he prepares for high stakes nuclear diplomacy, said Larry Kudlow, chief economic adviser to the president, on Sunday.

He was speaking as Mr Trump touched down in Singapore aboard Air Force One, a few hours after Kim arrived with his entourage.

Trailing in his wake was the turbulence of a G7 summit all but sabotaged by a pair of incendiary tweets aimed at Justin Trudeau, the Canadian prime minster, describing him as “dishonest” and “meek”, as well as ordering his officials not to sign a joint statement on trade, Iran and climate change.

He continued the offensive on Monday, saying "Justin acts hurt when called out!".