Trump suggested he might have skipped the upcoming summit entirely were it not being hosted by Turkish President Recep Tayyip Erdogan.

Since his first term, Trump has accused European allies of not investing enough in their own militaries and relying too heavily on U.S. contributions.

NATO Secretary-General Mark Rutte is working to keep the alliance united and Donald Trump engaged. But disputes over burden sharing, US military commitments, and the Iran war are…