Trump calls Trudeau 'two-faced' after viral video

US President Donald Trump has called Canadian counterpart Justin Trudeau "two-faced" after footage emerged of world leaders mocked him.

The video, which has gone viral, shows Trudeau, UK Prime Minister Boris Johnson, French President Emmanuel Macron and Dutch Prime Minister Mark Rutte appearing to have a laugh about Trump's behaviour at the summit. 

During his media interaction before a meeting with German Chancellor Angela Merkel, Trump attributed Trudeau’s frustration to the pressure to increase Canada’s military spending to 2 per cent of its economic output.

"He should be paying more than he's paying," Trump said. "I called him out on that and I’m sure he wasn’t happy about it, but that’s the way it is."

Trump later took to Twitter to announced he was skipping the closing news conference and was leaving the NATO summit early.