US President Donald Trump on Tuesday voiced disappointment with the response of Nato allies to Washington’s recent military campaign against Iran, saying the conflict had served as a test of the alliance’s willingness to support the US in times of crisis. Speaking alongside Turkish President Recep Tayyip Erdogan after arriving in Ankara for the Nato summit, Trump questioned whether European allies would offer the same level of support to the US that Washington has historically provided to them.

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.

The two-day gathering in Ankara comes a year after NATO members pledged to ramp up security-related spending to 5% of GDP under pressure from the US leader. Yet, the US President…