Trump joins NATO summit amid Ukraine, spending tensions
The US president is due to hold talks with his Turkish counterpart, Recep Tayyip Erdogan, at his sprawling presidential palace before joining an official leaders' dinner ahead of the main session of the summit on Wednesday.
Trump made his first foreign flight aboard his new Qatari-gifted Air Force One plane. He was greeted on the tarmac by Erdogan and a presidential guard, some dressed in blue, others in red.
Ahead of his arrival, NATO allies have tried to showcase surging defence spending with new arms contracts worth billions in an effort to placate the mercurial US leader's fury over Europe's response to the war with Iran.
The two-day gathering comes a year after NATO members pledged to ramp up security-related spending to five percent of GDP under pressure from the US leader.
Opening the summit, NATO Secretary-General Mark Rutte called for a "transatlantic defence industrial revolution", saying member states had invested $37bn in additional defence spending over the past year.
Rutte said the alliance would have the capacity to produce four million artillery shells annually by next year, urging defence industries to accelerate production and convert increased spending into military capability.
The summit comes amid renewed debate over NATO's future after Trump again criticised allies for insufficient defence contributions and previously said he was considering withdrawing the United States from the alliance.
Ukraine is expected to dominate discussions, with Zelenskyy saying "important work lies ahead" and calling for decisions on air defence systems, missiles and production licences.
Russia, meanwhile, said it would closely monitor the outcome of the summit, describing recent NATO statements as confrontational while maintaining that diplomatic contacts with Washington remain open.