Starmer will give a speech at the Munich Security Conference on Saturday.
The prime minister is expected to say he is "talking about a vision of European security and greater European autonomy" that is not about "an American withdrawal but about responding to the call for more burden-sharing."
He is also expected to say that there is "no British security without Europe, and no European security without Britain."
From a European perspective, there is uncertainty about whether the United States, led by President Donald Trump, will continue to be a guarantor of security in Europe.
