THE HAGUE, Netherlands >> The head of the NATO military alliance warned Monday that no country could have an opt-out from a massive new hike in defense spending, and that progress they make toward reaching the new target will be reviewed in four years.

At a summit in the Netherlands on Wednesday, NATO leaders are expected to endorse a goal of spending 5% of their gross domestic product on their security, to be able to fulfil the alliance’s plans for defending against outside attack.

“NATO has no opt-out, and NATO does no side deals,” NATO Secretary-General Mark Rutte told reporters in The Hague. “It is critical that each ally carries their fair share of the burden.”

However, Spain said that it has reached a deal with NATO to be excluded from the 5% target, while President Donald Trump said the figure shouldn’t apply to the United States, only its allies.

In announcing Spain’s decision Sunday, Prime Minister Pedro Sánchez said the spending pledge language in NATO’s final summit communique — a one-page text of perhaps half a dozen paragraphs — would no longer refer to “all allies.”

It raises questions about what demands could be insisted on from other members of the alliance like Belgium, Canada, France and Italy that also would struggle to hike security spending by billions of dollars. Rutte conceded that for some, reaching 5% will “still be a long road ahead.”

On Friday, Trump insisted the U.S. has carried its allies for years and now they must step up.

NATO’s new spending goals

The 5% goal is made up of two parts. The allies would agree to hike pure defense spending to 3.5% of GDP, up from the current target of at least 2%, which 22 of the 32 countries have achieved. Money spent to arm Ukraine also would count.

A further 1.5% would include upgrading roads, bridges, ports and airfields so armies can better deploy, establishing measures to counter cyber and hybrid attacks and preparing societies for future conflict.

The second spending basket is easy for most nations, including Spain. Much can be included. But the 3.5% on core spending is a massive challenge.

Last year, Spain spent 1.28% of GDP on its military budget, according to NATO estimates, making it the alliance’s lowest spender. Sánchez said Spain would be able to respect its commitments to NATO by spending 2.1% of GDP on defense needs.

Spain also is among Europe’s smallest suppliers of arms and ammunition to Ukraine, according to the Kiel Institute, which tracks such support. It’s estimated to have sent about 800,000 euros ($920,000) worth of military aid since Russia invaded in 2022.

Beyond Spain’s economic challenges, Sánchez has other problems. He relies on small parties to govern and corruption scandals have ensnared his inner circle and family members. He is under growing pressure to call an early election.

Setting a deadline

It’s not enough to agree to spend more money. Many allies haven’t yet hit an earlier 2% target that they agreed in 2014 after Russia annexed Ukraine’s Crimean Peninsula. So the incentive of a deadline is required.

The U.S. insists it cannot be an open-ended pledge and a decade is too long. Still, Italy says it wants 10 years to hit the 5% target.

The date of 2032 was initially floated, but 2035 appears to be the year that will be settled on. An official review of progress is likely to be conducted in early 2029, just after elections are scheduled to take place in the United States.