US Secretary of State Marco Rubio has sought to reassure a nervous Europe, saying that the United States wanted to "revitalise" the transatlantic alliance so that a strong Europe could help the US on its mission of global "renewal".

"Our freedom is not guaranteed" in an era of big powers, the German chancellor tells Munich's security summit.

"Our freedom is not guaranteed" in an era of big powers, the German chancellor tells Munich's security summit.

German Chancellor Friedrich Merz opened the Munich Security Conference by describing a geopolitical landscape bereft of former signposts, saying the old world order "no longer exists," warning of threats posed by Russia and China, and suggesting US-Europe ties must be fixed.