Frank-Walter Steinmeier, speaking after a meeting with alliance Secretary-General Jens Stoltenberg in Brussels, said Trump's remarks contradicted views expressed by designated Defense Secretary James Mattis. He spoke also of "amazement".
"I've spoken today not only with EU foreign ministers but NATO foreign ministers as well and can report that the signals are that there's been no easing of tensions," Steinmeier told reporters when asked about Trump's interview with Bild newspaper and the Times of London.
"Obviously the comments from President-elect Trump, that he views NATO as obsolete, were viewed with anxiety," he said.
Trump, who is due to be sworn in as president on Friday, said NATO was obsolete because it had not defended against terrorist attacks.