US President Donald Trump has landed in the Turkish capital Ankara to attend a two-day NATO summit.
Trump said he was "very disappointed" by the response of NATO allies in Europe to his war with Iran after arriving for the alliance's summit.
"I was very disappointed with NATO," Trump told journalists as he met Turkey's President Recep Tayyip Erdoğan.
"We didn't need any help at all, and in a way, I was testing people, I was testing to see whether or not they'd be there, because I've long said that we helped them, but I'm not sure that they'd be there for us."
NATO allies showcased surging defence spending with new arms contracts worth billions at a summit in Turkey on Tuesday as they sought to placate US President Donald Trump's fury over Europe's response to the war with Iran.
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.
NATO chief Mark Rutte has insisted European countries are "delivering" by bolstering military budgets and moving to take more responsibility for the defence of their continent in the face of Russia.
In bid to impress Trump before he touched down, NATO kicked off with a string of arms announcements at a glitzy defence industry forum ahead of the main summit.
"Allies and industry from both sides of the Atlantic will reveal new major projects and sign contracts worth literally billions of dollars," Rutte said.
"These are billions that are invested in our security, boosting our economies and supporting hundreds of thousands of new jobs."
Among the initial deals announced were contracts for new drones, refuelling, and surveillance aircraft designed to bolster Europe's ability to protect itself.
But Trump, still smarting after European countries restricted US forces from using bases to attack Iran, has spent the run-up to the summit slamming allies for not moving fast enough for his liking.
"Ridiculous for the U.S.A. to continue along this one-sided path when the relationship is not reciprocal. They were not there for us!!!" Trump wrote on Truth Social last week.
'Real shift'
European leaders are aiming at least to avoid a bust-up with the mercurial US leader that could deal a further blow to NATO's credibility after Trump repeatedly cast doubt on Washington's commitment to protecting its allies.
Diplomats are banking on Trump's good relationship with Turkish leader Recep Tayyip Erdoğan and an unstinting charm offensive by NATO chief Rutte, to keep his mood in check.
But with Trump having had fallings out with a string of other leaders, most recently Italy's Giorgia Meloni, there are plenty of irritants that could ignite his anger.
Seeking to show willingness on Iran, European allies spearheaded by France and Britain have put together a potential naval mission to help in the Strait of Hormuz and countries have shifted vessels closer to the region to be ready.
But the situation remains volatile and the Europeans want clarity on how a fragile US deal with Iran is panning out before sending in their navies.
While they will be hoping that Trump strikes a conciliatory tone, European leaders have begun to come to terms with the reality that the US is inexorably pulling back from their alliance.
Washington has been clear it wants its allies to take the lead on the conventional defence of the continent and recently announced it was cutting back the assets it makes available to NATO commanders.
European nations will look to prove they're ready to play a greater role while also trying to keep Trump, and the vast might of the US military, as engaged as possible.
"All of this is evidence of a real shift in mindset," Rutte said. "This is NATO 3.0. A stronger Europe in a stronger NATO."
