Mr Trump placed his right hand on Montenegro Prime Minister Duško Markovic's arm, abruptly pushing him aside to position himself front-and-centre among a group of North Atlantic Treaty Organisation (NATO) leaders as they prepared for a group photograph inside the alliance's new headquarters.
His comments come hours after reports emerged in German media that U.S. President Donald Trump described Germans as "very bad" and threatened to block German auto imports to the U.S.
The act was being widely denounced online.
"Many of these countries owe massive amounts of money from past years", he said, adding that the target they had committed to - two per cent of each country's GDP to be spent on defence - was merely "the bare minimum".
The rebuke was being criticized by opponents.
The NATO summit is Trump's second-to-last stop in his first worldwide trip as president.
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President Trump has ordered the Justice Department to investigate the source of those leaks. But according to Gary Cohn, whose role as National Economic Council director involves cleaning up his boss's messes, Trump totally didn't mean what he said. During a photo-call, none of the heads of government could bring themselves to speak to Mr Trump, preferring to huddle round Angela Merkel.
"Wow. Trump shoves Montenegro's leader to get to the front of the group at NATO Summit", said another user. While all administrations deal with some leaks, news outlets have been privy to everything from details of draft documents to the president's private phone conversations with foreign leaders.
"The leaders of the Middle East have agreed at this unprecedented meeting to stop funding the radical ideology that leads to this awful terrorism all over the globe", Trump said. No NATO leaders were seen approaching Trump to speak with him on his way out.
"Some issues remain open, like climate and trade".
NATO's chief affirmed that the alliance would join the global coalition fighting the Islamic State of Iraq and the Levant (ISIL) group, but will not wage direct war against the extremists. An anti-terror coordinator may also be named. He treated French President Emmanuel Macron to the world's most awkward handshake.
White House spokesperson Sean Spicer, when asked about Trump moving past Markovic, said he had not seen the video but assumed the United States president was moving to his designated spot. Both men's jaws seemed to clench.