Donald Trump has been ridiculed on social media for appearing to push Montenegro Prime Minister Dusko Markovic out of the way to get to the front of a group of Nato leaders.
Trump's shoving got the attention of the other leaders, who watched as he adjusted his jacket and appeared to have a smug smile on his face after the altercation.
Trump has not hidden his disdain for Nato, which he has called "obsolete" because it is not addressing "taking care of terror".
In an address to other Nato leaders he lectured them on needing to pay their "fair share" in the alliance.
The press pool reports that Trump and the other Nato leaders subsequently "ignored one another" during "family photo" ops in Brussels.
The shove is likely to become another viral moment from Trump's first overseas trip as president. Earlier in the trip First Lady Melania Trump can be seen swotting away his attempts to hold her hand.