The Hague (Netherlands) | NATO Secretary-General Mark Rutte was upbeat that the military organisation will agree on massive spending hikes at a “transformational summit” on Wednesday, as member state leaders including US President Donald Trump assembled in The Netherlands.

Leaders of the 32-nation alliance are expected to agree a new defense spending target of 5 per cent of gross domestic product, as the United States — NATO's biggest-spending member — shifts its attention away from Europe to focus on security priorities elsewhere.

“So a transformational summit. Looking forward to it,” Rutte told reporters in The Hague, before chairing the meeting's only working session, which was expected to last less than three hours.

But ahead of the meeting, Spain announced that it would not be able to reach the target by the new 2035 deadline, calling it “unreasonable”.

Belgium signalled that it would not get there either, and Slovakia said it reserves the right to decide its own defence spending.

Rutte conceded that “these are difficult decisions. Let's be honest. I mean, politicians have to make choices in scarcity. And this is not easy.” But he said: “given the threat from the Russians, given the international security situation, there is no alternative”.

Other countries closer to the borders of Russia and Ukraine — Poland and the three Baltic countries — have committed to the goal, as have NATO's European heavyweights Britain, France, Germany and the Netherlands.

On Tuesday, Trump complained that “there's a problem with Spain. Spain is not agreeing, which is very unfair to the rest of them, frankly”.

He has also criticized Canada “a low payer.” In 2018, a NATO summit during Trump's first term unravelled due to a dispute over defense spending.

After Russia's full-scale invasion of Ukraine in 2022, the NATO allies agreed to make 2 per cent of GDP the minimum spending level. Last year, 22 countries were expected to hit that target, up from just three a decade ago.