Republican Senator John McCain broke with the reassuring message that U.S. officials visiting Germany have sought to convey on their debut trip to Europe, saying on Friday that the administration of President Donald Trump was in "disarray".
McCain, a known Trump critic, told the Munich Security Conference that the resignation of the new president's security adviser Michael Flynn over his contacts with Russia reflected deep problems in Washington.
"I think that the Flynn issue obviously is something that shows that in many respects this administration is in disarray and they've got a lot of work to do," said McCain.
"The president, I think, makes statements (and) on other occasions contradicts himself. So we've learned to watch what the president does as opposed to what he says," he said.
European governments have been unsettled by the signals sent by Trump on a range of foreign policy issues ranging from NATO and Russia to Iran, Israel and European integration.
The debut trip to Europe of Trump's Defence Secretary Jim Mattis and Secretary of State Rex Tillerson, to a meeting of G20 counterparts in Bonn, went some way to assuaging concerns as they both took a more traditional U.S. position.
But Trump is wrestling with a growing controversy at home about potential ties between his aides and Russia, which he dismissed on Thursday as a "ruse" and "scam" perpetrated by a hostile news media.