THIS week the North Atlantic Treaty Organisation (NATO) held its first meeting of defence ministers since Donald Trump became America′s president. Many of the group′s 28 members grew nervous after Mr Trump called it “obsolete” during his campaign, and suggested that the United States would only provide military aid to a threatened member if it had paid its fair share. The president has tamped down such rhetoric of late. Nonetheless, on February 15th America’s defence secretary, James Mattis, warned allies that they must adopt plans to raise their military spending or risk seeing its most powerful member “moderate its commitment to the alliance”.

The United States has a point in noting that its commitment is disproportionately large. Last year it spent 3.6% of its GDP on defence, the highest ratio of any NATO member (and the highest total military budget in the world by a hefty margin). That is almost double the target of 2% of GDP that NATO members all agreed to in 2006. At the time six members reached the threshold; last year five did.

Such gripes are hardly new. Since the 1970s numerous American presidents have complained about military “free-riding” by the country′s European allies. The differences between NATO members′ defence budgets grew larger following the end of the cold war, as some countries rushed to claim a peace dividend faster than others. Budget-tightening after the 2008 financial crisis has continued the trend.

At a summit in 2014, NATO reiterated its commitment to the 2% target. Members that fell short at the time promised to meet their obligations by 2024. Some have duly ramped up military spending since. However, they are mostly in eastern Europe, where the threat from Russia is felt most keenly. These countries also tend to have relatively small economies by NATO standards. Estonia and Poland now meet the target, and Latvia and Lithuania are on course to do so. In contrast, some of the alliance′s bigger and richer members remain resistant to pulling their weight. Germany, which has more fiscal room for manoeuvre than any other NATO country, spends just 1.2% of its GDP on defence. Spain and Italy have also cut their military budgets to around 1% during the past decade. They would struggle to satisfy NATO while observing restrictive European Union budget rules.

The summit ended with a mild show of solidarity, as France, Germany, Belgium and Norway announced plans to buy jets and submarines jointly. Nonetheless, American complaints about paying more than its fair share are likely to grow louder.