Trump has never said he opposed NATO. His issue is the money and mission. He doesn't object to NATO, he objects to these wealthy countries refusing to pay their fair share of it. He wants to renegotiate the cost. Same with South Korea and Saudi Arabia. He also thinks they need to worry less about Russia and more about Terrorists. When asked, he said if NATO members won't pay their bills and carry more of the load, then we'll consider withdrawing, because we can't afford to keep this up.