But according to a former U.S. ambassador to NATO, Trump's statements are misleading.
"There is no ledger sheet that shows Germany in the red," Doug Lute, who served as ambassador under President Obama from 2013 to 2017, told ABC News. "That's not how it works in NATO."
The alliance's roughly $2 billion operating budget is paid for by fixed apportions across the 28 NATO members. (The United States, for example, contributes the most: about 22.14 percent of that $2 billion annually. Germany comes in second, supplying 14.65 percent.)
German Defense Minister Ursula von der Leyen said, "There is no debt account in NATO."
However, NATO asks its members to spend at least 2 percent of their GDP on national defense.
Since the early 2000s, the U.S. has routinely budgeted 3 to 5 percent of its GDP for defense.
But like many other NATO countries — including Canada, Spain and Italy — Germany hasn't been spending 2 percent of its GDP on defense.
However, as Merkel affirmed Friday, the nation has promised to meet the 2 percent minimum for the next seven years, at least. "We committed to this 2 percent goal until 2024," she told reporters during a joint press conference at the White House.
Technically, Germany doesn't owe NATO money. Rather, the nation owes it to the alliance to spend more on its national defense.
"What we all want is a fair burden sharing," von der Leyen said in a statment. "In order to achieve that, we need a modern understanding of security, including a modern NATO, but also a European defense organization as well as investment in the United Nations."
ABC News' Katherine Faulders contributed to this report.