Washington (CNN) Once again, President Donald Trump is blasting NATO allies for failing to pay enough for their defense. And once again, by mistake or design, Trump isn't getting NATO funding quite right.

"The US is paying for Europe's protection, then loses billions on Trade. Must pay 2% of GDP IMMEDIATELY, not by 2025," the President tweeted from Brussels, Belgium, where he is meeting with other NATO leaders at an annual summit.

Trump had been on a tear even before he arrived in Brussels, declaring Tuesday that "many countries in NATO, which we are expected to defend, are not only short of their current commitment of 2% (which is low), but are also delinquent for many years in payments that have not been made. Will they reimburse the U.S.?

What good is NATO if Germany is paying Russia billions of dollars for gas and energy? Why are there only 5 out of 29 countries that have met their commitment? The U.S. is paying for Europe's protection, then loses billions on Trade. Must pay 2% of GDP IMMEDIATELY, not by 2025. — Donald J. Trump (@realDonaldTrump) July 11, 2018

Again and again, Trump has pushed the idea that allies in the North Atlantic Treaty Organization owe the US money. That's not how alliance funding works.

Here's how it does:

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