According to Jaap de Hoop Scheffer, the former NATO head, the 2 percent is an informal guideline.

Only six of the allies meet the informal, admittedly informal, two percent GDP benchmark. Only half of the allies make the 20 percent they should spend on new equipment.

Aviation Week reported earlier this year that NATO Funding Disparity Persists:

European NATO members continue to spend, on average, well under 2 percent of gross domestic product (GDP) on defense, according to new figures provided by the Atlantic alliance.

The average for European allies is 1.7 percent, whereas the U.S. GDP allotment in 2008 was 4 percent, NATO says. The U.S. spends by far more per-capita on defense than any other NATO members. In fact, the U.S. last year spent about 44 percent more on defense than all other NATO members combined.

An informal one, but one US diplomats have hammered European NATO allies over -- since Clinton I at least. Usually in the context of orders for the US mil-ind complex; and the US's assuaging by European vassals usually took the form of pointless fighter jet orders. Things got more complicated when the preference in jets became Eurofighters or Gripens.

I wish though that our NATO-member governments would stop playing tricky vassals who go along in US adventures but sabotage the effort, and just stopped going along, now THAT would deserve to be called neopacifism...

_{*Lunatic*, n.
One whose delusions are out of fashion.}