US Secretary of State Mike Pompeo has warned of the dangers posed by Russia and China, and called on Nato to grow and confront "the challenges of today".
On a visit to Berlin, Pompeo said methods used by China to suppress its own people would be "horrifyingly familiar" to East Germans.
And he accused Russia of invading its neighbours and crushing dissent.
He also laughed off comments from French President Emmanuel Macron, who said recently that Nato was "brain dead".
But Pompeo told reporters: "Seventy years on... it needs to grow and change. It needs to confront the realities of today and the challenges of today.