The release of the new estimates came after Donald Trump rattled the alliance by saying he would "encourage" Russia to attack members who were not meeting the obligation.

NATO's secretary general told journalists that the number of states reaching the target had increased sharply from 11 last year.

"That is another record number and a six-fold increase from 2014 when only three allies met the target," Stoltenberg said.

Overall European allies and Canada will have added more than $600 billion to their defence spending since they set the two-percent target a decade ago, he said.

Spurred on by Russia's all-out invasion of Ukraine in 2022, last year saw an "unprecedented rise" of 11 percent of spending by European members and Canada, the NATO chief added.

Stoltenberg reiterated a warning to Trump not to "undermine" NATO's collective security guarantee that all allies will help defend any member attacked.

"We should leave no room for miscalculation or misunderstanding in Moscow, about our readiness and our commitment, our resolve to protect allies," he said.