A "family photo" from the NATO summit in Brussels perfectly captures the awkwardness and tensions overshadowing this year's gathering.

President Donald Trump has consistently attacked his NATO allies for their spending levels and trade practices on Twitter in the weeks leading up to the summit.

European Union President Donald Tusk told Trump: "Appreciate your allies, after all, you don't have that many."

World leaders are currently gathered in Brussels, Belgium for the 2018 NATO summit, and after last month's rocky G7 summit, there are no shortage of tensions to be resolved.

This "family photo" of NATO members looking uncomfortable and askance in different directions seem to perfectly capture the significant differences in opinion and conflicts overshadowing the summit.

While the United States and Europe have historically been close military and economic allies, President Donald Trump has upended that order by repeatedly taking Europe to task over defense spending and trade while pursuing a closer US relationship with adversary Russian President Vladimir Putin.

In the photo were: German Chancellor Angela Merkel, Belgian Prime Minister Charles Michel, NATO Secretary General Jens Stoltenberg, Trump, and British Prime Minister Theresa May.

While on his way to the summit, Trump fired off a series of confrontational tweets accusing his NATO allies of stiffing the US by not paying their fair share to contribute to NATO's budget, and lamenting the trade imbalance between the US and the European Union.

"NATO benefits Europe far more than it does the US," Trump wrote. "By some accounts, the US is paying for 90% of NATO, with many countries nowhere close to their 2% commitment. On top of this the European Union has a Trade Surplus of $151 Million with the US, with big Trade Barriers on US goods. NO!"

Currently, NATO members are encouraged to put a target of 2% of their economic output towards their defense budgets and 1% of defense spending to fund NATO, but the those target numbers are just guidelines. There isn't a penalty for not meeting them, but Trump has repeatedly castigated Germany in particular for not spending enough, in his view, on defense.

Before the summit, European Union President Donald Tusk hit back at Trump for his "daily" criticisms of Europe, pointing out that the EU spends more on defense than Russia and almost as much as China, and telling him to "appreciate your allies. After all, you don't have that many."

Tusk and other NATO members are also concerned about the security implications of Trump's friendly relationship with Putin, who he publicly praises more than his European partners. Trump and Putin are set to meet on July 16 in Finland.