Spain insists it got an opt-out from NATO’s new goal of spending 5 percent of gross domestic product on defense, but alliance chief Mark Rutte on Monday raised questions about how low Spain will be able to go.

NATO allies agreed over the weekend on a new 5 percent of GDP goal by 2035 — with 3.5 percent going on “hard defense” such as weapons and troops, and an additional 1.5 percent on defense-related investments such as cybersecurity and military mobility. The document’s wording permits Spain to spend less as long as it meets the updated capability targets approved by alliance defense ministers on June 5.

Spanish Prime Minister Pedro Sánchez insisted on Sunday that Madrid would need to spend only 2.1 percent of GDP “to acquire and maintain all the personnel, equipment, and infrastructures requested by the alliance to confront these threats with our capabilities.”

Rutte thinks that’s very unlikely.

“Spain thinks they can achieve those targets with 2.1 percent spending. NATO is absolutely convinced that Spain will have to spend 3.5 percent to get there,” Rutte said at his Monday press conference in The Hague, ahead of the NATO leaders’ summit on Tuesday and Wednesday.

“NATO has no opt-out and NATO doesn’t know side deals,” Rutte said.

He stressed that each country will now regularly report on their progress in reaching the top secret capability targets. “So we will see, and anyway, there will be a review in 2029,” Rutte said.

Spain’s pushback against the 5 percent target has also inspired other countries with low defense spending to look for similar exemptions. On Monday, Belgium announced that it would seek “maximum flexibility” from NATO.

“We may not have done so by making a noisy statement like Spain, but I can assure you that for weeks our diplomats have been working hard to obtain the flexibility mechanisms,” Foreign Minister Maxime Prévot told local media. 

Last week, the country’s prime minister, Bart De Wever, told lawmakers that the Belgian government would support NATO’s new defense spending target, even though it is a “bitter pill to swallow.”