Nato leaders have agreed to ramp up defence spending to 5% of their countries' economic output by 2035, following months of pressure from Donald Trump.

The US president described the decision, taken at a summit in The Hague, as a "big win for Europe and... Western civilisation".

Members said in a joint statement that they were united against "profound" security challenges, singling out the "long-term threat posed by Russia" and terrorism.

Nato leaders reaffirmed their "ironclad commitment" to the principle that an attack on one Nato member would lead to a response from the full alliance.

However, the statement did not include a condemnation of Russia's invasion of Ukraine, as it had a year ago.

"No-one should doubt our capacity or determination should our security be challenged," said Nato Secretary General Mark Rutte. "This is a stronger, fairer and more lethal alliance that our leaders have begun to build".

The US president had earlier appeared to raise questions about the security guarantee, referring to "various definitions of Article Five". But Trump said after the summit: "I stand with [Article Five], that's why I'm here."

The Hague summit has been described by several leaders as historic, and Rutte said decisions made on Wednesday would include continued support for Ukraine while pushing for peace.

The commitment to raise defence spending over 10 years involves at least 3.5% of each member state's GDP on core defence expenditure by 2035, plus up to 1.5% on a broadly defined series of investments loosely connected to security infrastructure.

The US president hailed the summit - the first he has attended since 2019 - as a "big success".

He had said earlier that the hike in spending would be a "great victory for everybody, I think. We will be equalised shortly, and that's the way it has to be".

Spain in particular had objected to the 5% target ahead of the meeting. Economy Minister Carlos Cuerpo said Madrid was making an "enormous effort" to reach a target of 2.1% and "the discussion about the percentage is misguided".

As the leaders gathered for the traditional "family photo", Spanish Prime Minister Pedro Sánchez appeared to stand by himself at the far end of the group.

Nevertheless, Sánchez later went ahead and signed Nato's statement, maintaining that it was "sufficient, realistic and compatible" for Madrid to meet its commitments while paying less.

The Belgian government had also expressed reservations, but Prime Minister Bart de Wever told reporters that while it would not be easy, "3.5% within 10 years is a realistic goal".

Slovakia had also raised concerns about the big hike in defence spending, but President Peter Pellegrini indicated that Bratislava would not stand in the way.

French President Emmanuel Macron took issue with Trump's trade tariff confrontation with the European Union and called for a deal.

"We can't say to each other, among allies, we need to spend more... and wage trade war against one another, it makes no sense," he said.

The Hague summit, which began with a dinner on Tuesday night hosted by King Willem-Alexander and Queen Maxima, was scaled back so Wednesday's set-piece gathering of leaders was due to last only two and a half hours.

Rutte told Nato leaders that they were meeting at a "dangerous moment", and that the defence alliance's guarantee of mutual defence "sends a powerful message".

Rutte also praised Trump for his handling of the Iran-Israel conflict, and referenced the president's use of an expletive when describing his frustration at signs a ceasefire announced hours earlier could be in jeopardy on Tuesday.

Speaking at the summit, Trump said the two countries had fought like "two kids in a schoolyard", and Rutte interjected: "And then daddy has to sometimes use strong language."

The US president also spoke to Ukraine's Volodymyr Zelensky on the sidelines of the summit. During a news conference afterwards, Trump said achieving a ceasefire in Ukraine was proving "more difficult" than he had expected, and raised the prospect of supplying Ukraine with further air defences.

"He's got a little difficulty, Zelensky, a nice guy," said Trump. "I've spoken to Putin a lot... he volunteered help on Iran. I said do me a favour, help us on Russia, not Iran."

In their final communique, Nato member states stressed their commitment to providing support for Ukraine, "whose security contributes to ours", adding that direct contributions to Kyiv's defence and its defence industry would be included in assessment of allies' defence spending.

UK Prime Minister Sir Keir Starmer said Nato was as relevant and important now as it had ever been: "We live in a very volatile world and today is about the unity of Nato, showing that strength. We're bigger than we were before, we're stronger than we were before."