The North Atlantic Treaty Organization, the defense alliance of 32 countries, is on a spending spree, with plans to funnel billions into their militaries and security systems over the coming decade.

But it’s a splurge that some European members of NATO, grappling with huge and ballooning debt burdens, can ill-afford.

“It’s something unprecedented in peacetime to have such a massive increase in spending on any item – in particular, on defense,” Marcel Fratzscher, president of the German Institute for Economic Research or DIW, told CNN.

Last month, NATO members agreed to boost their respective defense spending targets to 5% of gross domestic product by 2035 – more than double the current 2% target and the sort of major increase that US President Donald Trump has been demanding for many years.

The pledge came as Europe’s NATO members have to contend with an aggressive Russia and an America that has backed away from its long-standing role as the guarantor of the region’s security.