The small Balkan state was set for a warm welcome into the military alliance, as its 29th member, this week at the summit in Brussels but appeared to have been given the cold shoulder.
In the clip, the US leader – a staunch critic of Nato – is seen grabbing Duško Marković from behind and pushing in front of him from within a crowd of world leaders.
He then adjusts his blazer and looks around before continuing to talk to his fellow Nato leaders.
Video of the shove has since gone viral on social media, with almost 12,000 retweets on Twitter.
Donald Trump appeared to shove Duško Marković at the Nato summit
Twenty-three of the 28 member nations are still not paying what they should be paying
“He's like a child trying to be king of the playground, but all the other kids are actually adults. He looks foolish,” said one angry user.
Another added: “It's obvious they were deliberately ignoring him and he felt uncomfortable. He's not respected by any of them and he's feeling it!”
President Trump later berated European leaders in a speech reminding them of their commitment to spend at least two per cent of GDP on military budgets.
He said: “I have been very, very direct… in saying that Nato members must finally contribute their fair share and meet their financial obligations.
NATO countries' heads of states gather in Brussels
Thu, May 25, 2017
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NATO countries' heads of states and governments gather in Brussels for a one-day meeting
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U.S. President Donald Trump and Britain's Prime Minister Theresa May react during a ceremony at the new NATO headquarters in Brussels
Donald Trump ruffled a few feathers at the Nato summit
“But 23 of the 28 member nations are still not paying what they should be paying and what they’re supposed to be paying for their defence.”
He said Nato’s reliance on America money was “unfair”.
Mr Trump continued: “This is not fair to the people and taxpayers of the United States and many of these nations owe massive amounts of money from past years and not paying in.
“Over the last eight years, the United States spent more on defence than all other Nato countries combined.
“If all Nato members had spent just two per cent of their GDP on defence last year, we would have had another $199billion for our collective defence.”