NATO allies are expected to discuss Trump’s demand that members increase their defense spending, the organization’s support for Ukraine against Russia, and the U.S. war with Iran.

President Trump landed Tuesday in the Turkish capital, Ankara, for a NATO summit, where the focus will be on what other countries in the alliance have done about his demand to increase military spendi...

NATO Secretary General Mark Rutte has attempted to temper tensions, declaring that European allies have heeded calls from the U.S. to take on a greater burden.