Former President Trump said he would "100%" keep the U.S. in NATO if he returns to the presidency so long as European countries pay their "fair share" and "play fair."

Why it matters: The presumptive GOP presidential nominee has long been critical of the defensive alliance, leading to questions about whether he would try to pull the U.S. out if re-elected.

What he's saying: "The United States should pay its fair share, not everybody else's fair share," Trump told Nigel Farage, the Brexit campaigner turned Trump ally, in an interview that aired Tuesday on GB News.

• Trump told the conservative U.K. news network that he believes the U.S. "was paying 90% of NATO," calling it the "most unfair thing."
• The former president also said NATO "has to treat the U.S. fairly," arguing that if not for the U.S., NATO "literally doesn't even exist."
• "It's more important for [European countries] than it is to us. We have an ocean in between [us and] some problems," Trump said. "They took advantage of us on trade."

Flashback: During a February rally, Trump said he had told the leader of an unidentified NATO member that he would "encourage" Russia "to do whatever the hell they want" to countries who were not hitting the spending target, leading to widespread criticism.

• Trump addressed those comments in Tuesday's interview, calling them "a form of negotiation."

Reality check: NATO members do not pay "dues," as Trump often claims, but the alliance set a benchmark in 2014 for every country to spend at least 2% of GDP on their own defense.

• The alliance expects a record 18 of its 32 members to hit the 2% target in 2024, up from three who spent 2% a decade ago.
• Trump often takes credit for the increase, though Russia's invasion of Ukraine was a primary motivator for many European member states.
• The U.S. spent 3.5% of GDP on defense last year, and Washington's defense spending is two-thirds of the total spent by all member states.

Zoom out: Trump flirted with the idea of pulling out of NATO on multiple occasions during his time in the White House but never pursued withdrawal.

• There's a new obstacle in his way should he change course. Congress passed a bill in December to prevent a president from withdrawing from NATO without Congressional approval.

Go deeper: How Trump's NATO comments escalate his disdain for America's allies