ANKARA : NATO allies will showcase surging defence spending at a summit in Turkey's capital Ankara on Tuesday as they hope to placate US President Donald Trump after his fury over Europe's response to the war with Iran.

The two-day gathering at Turkey's sprawling presidential palace comes a year after NATO members pledged to ramp up security-related spending to five percent of GDP under pressure from the US leader.

NATO chief Mark Rutte insists European countries are "delivering" on their promise by bolstering military budgets and moving to take more responsibility for the defence of their continent in the face of Russia.

"Just one year later, we already see transformational progress," Rutte told journalists in Ankara on the eve of the summit.

In a bid to impress Trump, NATO has lined up a series of headline-grabbing figures.

"This is showtime," a senior European diplomat said, speaking on condition of anonymity.

At an industry forum on Tuesday ahead of the main summit, leaders are set to unveil new arms deals worth tens of billions to show Trump they're delivering on their words.

Underscoring that push, Canada announced on Monday that it had selected Germany's Thyssenkrupp Marine Systems to build its new fleet of submarines, a multi-billion-dollar programme Ottawa framed as part of a broader effort to deepen defence ties with European NATO allies.

But Trump -- still smarting after European countries imposed restrictions on US forces 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 the US commitment to protecting its allies.

Diplomats are banking on Trump's good relationship with Turkish leader Recep Tayyip Erdogan, 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 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'll 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."

- 'Strong decisions' -

Beyond taking greater responsibility for their own defence, European countries have also taken over the support of Ukraine almost entirely as Trump has wound back US aid.

President Volodymyr Zelensky -- who will attend the leaders dinner on Tuesday -- will score a commitment from his European backers at NATO to keep at least 70 billion euros ($80 billion) of military aid flowing to Kyiv each year in both 2026 and 2027.

Zelensky -- who is set to hold talks with Trump at the Ankara summit -- urged the alliance to take "strong decisions" on boosting Ukraine's air defences after a devastating Russian blitz killed nearly 30 people.

The Ukrainian leader will look to convince Trump -- who held a phone call with Russia's Vladimir Putin ahead of the gathering -- that Kyiv is turning the tide in the war and that he should pressure Moscow back into serious peace negotiations.