U.S. President Donald Trump hailed his "chemistry" with Turkish President Recep Tayyip Erdoğan as he arrived in Ankara for Tuesday's NATO summit, using the occasion to renew his criticism of European allies over their handling of the conflict with Iran.

Erdoğan personally welcomed Trump on the tarmac as the U.S. president stepped off Air Force One before leading a ceremonial motorcade through the largely empty streets of the Turkish capital, accompanied by an honor guard of riders on white horses.

The summit comes at a tense moment for the 77-year-old transatlantic alliance, with Trump repeatedly criticizing NATO allies and signaling a reduced U.S. commitment to European security.

"I was very disappointed with NATO," Trump said during talks alongside Erdoğan at the Turkish president's sprawling palace.

"Frankly, if the summit weren't being held in Türkiye, where my friend happens to be a very strong leader, a very strong person, it's possible that I wouldn't have attended."