NATO has taken over air defenses in Poland from the US just days before the inauguration of President-elect Donald Trump, according to a NATO spokesman, with questions looming about the incoming administration’s approach to the alliance and to Ukraine.

NATO’s new role as the command hub for air defense in Poland is the latest push to have the alliance shoulder more responsibility, U.S. Army Col. Martin O’Donnell, spokesman for Supreme Headquarters Allied Power Europe, said Monday.

Poland is backing Donald Trump’s call to NATO countries to spend 5 percent of their GDP on defense. Trump’s call for alliance members to more than double the target for defense budgets has prompted a mixed reaction among Europe’s cash-strapped governments.