His apprehension then stemmed directly from President Donald Trump's threat to pull the US out of NATO unless European nations sharply raised their defense contributions.
“We were all genuinely worried… we feared he might actually leave the meeting,” Jens Stoltenberg told CNN.
At the time, during his first term in the White House, Donald Trump had complained that NATO’s European members were not paying the alliance's target of two percent of GDP, and threatened to withdraw US support.
In his book, On My Watch, Leading NATO in a Time of War, the alliance's former chief said that without US backing, the NATO treaty and its security guarantees were "not worth much."
Shortly after that summit, European leaders pledged faster increases in defense spending, and, according to Stoltenberg, he "felt indescribable relief."