BRUSSELS — NATO Secretary General Jens Stoltenberg said Thursday that alliance members increased their defense spending in 2017 for a third consecutive year, amid complaints from President Trump that only a handful of the 29 allies are meeting their pledges.
The numbers were unlikely to allay Trump’s anger over his perception that Europe is taking the U.S. defense umbrella for granted. No additional countries met NATO’s defense spending goals last year, and only four — the United States, Britain, Estonia and Greece — reached the mark, although more are expected to get there in 2018.
Lagging European defense spending has frustrated U.S. officials for years, but in the Trump era, the numbers have taken on outsize importance.
Countries registering shortfalls face threats from Washington, including the prospect that the United States might not come to their defense. Some of Trump’s economic advisers have said that exemptions to new steel and aluminum tariffs might be granted only to countries that spend at least 2 percent on defense.
“All allies are stepping up, doing more in more places in more ways,” Stoltenberg said as he unveiled NATO’s annual report.
NATO countries — not including the United States — collectively spent an estimated 1.45 percent of their annual economic output on defense last year, still short of the 2 percent agreed to by national leaders in 2014 as a 10-year target.
That was the year Russia’s annexation of Ukraine’s Crimean Peninsula sparked fears in Europe that the continent was badly prepared for a traditional ground war with Russia, once NATO’s reason for being.
The report comes as Britain says it believes Russia carried out a nerve-agent attack on its soil this month, a case the alliance described as the first instance of chemical weapons being used offensively against a member nation since its founding after World War II.
British diplomats on Wednesday outlined their concerns about the attack to their NATO peers, but they stopped short of triggering a formal alliance response.
“The substance used is one of the most toxic ever developed,” Stoltenberg said. “The attack was a breach of international norms and agreements. This attack was unacceptable. It has no place in a civilized world.”
He added that the higher spending will help alliance members defend against and respond to chemical attacks of the type unleashed in Salisbury, which targeted a Russian who had spied for Britain.
This year, eight countries are expected to meet NATO’s 2 percent goal: Britain, Estonia, Greece, Latvia, Lithuania, Poland, Romania and the United States. In 2017, Poland narrowly missed the cut — at 1.99 percent of its annual economic output — after its economy grew faster than it had expected when it made its defense spending plans.
Under pressure from the United States, NATO members have pledged to create road maps of how they will meet the goals by 2024.
Before individual members’ defense spending turned back upward in 2015, the overall figure had been falling every year since 2008, in part because of the global economic crisis that struck around that time.
Policymakers who were involved in the 2014 negotiations that ended with the spending commitments said that the 2 percent figure was chosen in part to galvanize public discussion, not because it was a magic number that would signal NATO had reached a state of readiness.
“It was a judgment about what level could be set that was politically at least somewhat credible and at least somewhat achievable and therefore had some mobilizing power about it,” said Adam Thomson, who was British ambassador to NATO until 2016 and is now director of the European Leadership Network, a security-focused think tank.
“Nobody could quite have expected the way it has been taken up in such an unsophisticated fashion by Trump, but that, too, has had a real impact,” he said.
Leaders of countries that do not meet the goals sometimes say the raw numbers fail to fully capture defense commitments. Efficient spending and a willingness to contribute troops to NATO missions are also an important measure, some of them say. In Germany, which lags on hard military spending, leaders say their extensive development aid commitments contribute to global security.
The United States still spends the lion’s share on defense in the alliance — 68.7 percent of the total in 2017. That reflects its role as the foremost global superpower. The United States spent 3.57 percent of its overall economic output on defense last year.
Other countries have dramatically ramped up their spending, a reflection of U.S. pressure that started well before Trump was elected and a sense of vulnerability after the annexation of Crimea. Romania poured an extra 34.8 percent into its spending last year. Bulgaria, Latvia, Lithuania, Spain and Luxembourg also recorded significant jumps.
Although most countries have boosted their spending, a handful have made cuts. Belgium, a nation of 11 million that hosts NATO headquarters, cut defense spending by 0.73 percent last year, reducing its outlay in the area to 0.9 percent of its economic output. Greece and Britain also registered declines, although both are still meeting their pledges.