Theresa May will tell world leaders and politicians at the annual global security conference in Munich that Britain will continue to contribute to the security of Europe but a new security treaty needs to be reached.
During talks with Angela Merkel on Friday, Mrs May said both sides need to be "bold and ambitious" in framing their future relations.
"Those who threaten our security would like nothing more than to see us fractured", she will warn the security experts gathered in Germany on Saturday.
"I will reiterate that the United Kingdom remains unconditionally committed to European security and set up my vision for a unique partnership between the EU and the United Kingdom on defence, information sharing, security and law enforcement", she said.
She said it covers only about a third of financial services activities, it requires third countries to shadow new European Union laws and "equivalence" designations can be withdrawn by Brussels with 30 days' notice. 'But there is precedent for comprehensive, strategic relationships between the European Union and third countries in other fields, such as trade.
Theresa May has spent months calling for a deep and special economic partnership with the European Union after Brexit and now her focus turns to security. But the thrust of the British government's argument is that we should be a special case.
One said: "They are going down the route of mutual recognition".
Nevertheless, the Prime Minister will acknowledge that no non-EU country now has a security agreement that "captures the full depth and breadth of our existing relationship". But she said the German people still "deplore" the decision to leave in the first place.
Speaking at an worldwide conference in Munich, the Prime Minister will turn the tables on critics who have accused her of putting joint working to combat terrorism and organised crime at risk. So let our message ring out loud and clear: we will not let that happen.
"We will find other ways of influencing, more informal ways, but they will be less direct, less pronounced and probably less successful than they are now", he said.
May is set to make a speech on how she would like the UK-EU security relationship to work after Brexit.