Former President Donald Trump has claimed that during his presidency, he made thinly-veiled threats to NATO leaders, indicating the U.S. would not defend them against Russia if they failed to meet their financial commitments to the alliance. Trump described this approach as a negotiation tactic, suggesting that without the threat, NATO members might not have been motivated to pay. This stance has been controversial, as it treats NATO members more like clients of a private security company rather than allied nations. Trump's comments reflect his long-standing criticism of NATO's financial arrangements, where he has frequently argued that member countries are not fulfilling their obligation to spend 2% of their GDP on defense, a goal set for 2024.
Source:
https://www.independent.co.uk/news/world/americas/us-politics/trump-nato-russia-pay-protection-b2063520.html
https://www.politico.eu/article/trump-says-he-would-encourage-russia-to-attack-nato-members-that-dont-pay-enough/