Trump will attend the NATO summit this week in Turkey, where his anger with European allies over the Iran war could upend the U.S.-led alliance.

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.

Key discussions involve the F-35 fighter jet program, Turkey's S-400 Russian defense system acquisition and increased defense spending from NATO allies.