Frank-Walter Steinmeier, a vocal critic of Donald Trump elected as Germany's 12th postwar president on Sunday, predicted "difficulties" in relations with the U.S. as the global order is upended by the new administration in Washington.

Asked whether he would seek to improve relations with Russia, the Social Democrat, who served two stints as foreign minister under Chancellor Angela Merkel, said the world was confronting a "complete re-ordering of international relations."

"In the past we were always certain that we would have more difficult negotiating partners in the east," Steinmeier told broadcaster ZDF hours after he was overwhelmingly elected to the mostly ceremonial post by a special assembly. "Suddenly we're confronted with a situation in which we'll at the very least deal with uncertainty and also difficulties in trans-Atlantic relations."