US President-elect Donald Trump and NATO Secretary-General Jens Stoltenberg have spoken by telephone and agreed the "enduring importance" of the Western military alliance.

"The president-elect and the secretary general both underlined NATO's enduring importance, and discussed how NATO is adapting to the new security environment, including to counter the threat of terrorism," NATO said in a statement on Friday.

The two leaders also discussed defence spending and agreed that "progress has been made on fairer burden-sharing, but that there is more to do," in an apparent reference to the United States far greater outlay on its military to protect Europe.