"President-elect Donald Trump stated during the election campaign that he is a big fan of NATO," Stoltenberg said in Brussels as he arrived for talks with EU defence ministers.
"And I am certain that he will be a president... Who will live up to all the commitments of the United States in the alliance, because a strong NATO is important for Europe but it's also important for the United States."
He also appeared to be much more friendly towards Russia, praising President Vladimir Putin as a strong leader in marked contrast to a weak Barack Obama in Washington.
Asked about a telephone call between Trump and Putin on yesterday in which the Kremlin said they agreed to improve relations, Stoltenberg denied this was cause for concern.
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"First of of all, I think it is a very normal thing that president-elect Donald Trump speaks to world leaders, including of course the leader of Russia," he said.
Stoltenberg's upbeat tone came despite his stark warning in Britain's Observer newspaper on Sunday, in which he wrote that "going it alone is not an option... This is no time to question the partnership between Europe and the United States."
But the NATO chief noted today that the two sides were on the same page, saying Trump's call for the allies to increase defence spending was exactly what they were already doing.