London (CNN) US Secretary of State John Kerry has criticized President-elect Donald Trump for a newspaper interview in which he branded NATO "obsolete" and said Germany had pursued a "catastrophic" policy on refugees.

Kerry told CNN's Christiane Amanpour it was "inappropriate" for Trump to "be stepping in to the politics of other countries in a quite direct manner."

Trump's interview in the Times of London and the German publication Bild had rattled allies. The German foreign minister said it had caused "astonishment and agitation" within NATO.

JUST WATCHED Watch the full interview with Kerry Replay More Videos ... MUST WATCH Watch the full interview with Kerry 11:05

As well as repeating his criticism of NATO, Trump said the German Chancellor Angela Merkel had made a "catastrophic" mistake in accepting one million refugees. He also said sanctions on Russia for its annexation of Crimea could be eased in return for a deal to reduce nuclear weapons, and suggested his son-in-law Jared Kushner could lead a Middle East peace effort.

In his CNN interview, Kerry defended Merkel as "one of the strongest leaders in Europe" and "most important players with respect to where we are heading."