Theresa May offered a post-Brexit security partnership to Europe in a keynote address to a Munich security conference that has heard the continent was building its own military structures.
With other parts of the exit negotiations mired in uncertainty, London hopes a security treaty would entrench mutual co-operation under common goal of protecting European population against threats that do not recognise international borders.
The British leader proposed taking trade deals as a model for pragmatic security arrangement.
"The challenge for all of us today is finding the way to work together, through a deep and special partnership between the UK and the EU, to retain the co-operation that we have built and go further in meeting the evolving threats we face together,” she said.
"I recognise there is no existing security agreement between the EU and a third country that captures the full depth and breadth of our existing relationship.
"But there is precedent for comprehensive, strategic relationships between the EU and third countries in other fields, such as trade. And there is no legal or operational reason why such an agreement could not be reached in the area of internal security."
What was at stake was issues such as thwarting terror attacks and seamless extradition arrangements under the European arrest warrants.
“Those who threaten our security would like nothing more than to see us fractured,” she said. “They would like nothing more than to see us put debates about mechanisms and means ahead of doing what is most practical and effective in keeping our people safe. So let our message ring out loud and clear today: we will not let that happen. We will keep our people safe, now and in the years to come.”
Calling for political will to strike a separate agreement, Mrs May called for statesmanship in forging her proposed unique arrangements. Punishing Britain for leaving would be a self-harming option, she said.
“If the priority in the negotiations becomes avoiding any kind of new co-operation with a country outside the EU, then this political doctrine and ideology will have damaging real world consequences for the security of all our people, in the UK and the EU. As leaders, we cannot let that happen,” she said.
She also said the agreement could add to the suite of close partnerships Britain enjoys with other regions, including the Arabian Gulf.
"It is why we have created a highly developed set of security and defence relationships: with the US and Five Eyes partners, with the Gulf and increasingly with Asian partners too," she said.
Mrs May spoke to the European security forum a day after she met Chancellor Angela Merkel in Berlin to discuss the future economic ties between Britain and the EU. However there was little sign of progress.
“I want to say that I am not frustrated, I am curious how Great Britain imagines our relationship to be,” Mrs Merkel said at the end of the meeting.
The British exit from the EU, which is due to take place in March next year, has seen Germany throw its weight behind a European defence force. The drive has shifted the focus from the traditional Nato alliance with the US and Canada, prompting warnings from Washington that Brussels should not compete with the partnership.
The situation prompted blunt words from the Nato secretary general, Jens Stoltenberg, who told delegates that Europe alone could not defend itself. "European military co-operation is no alternative to Nato,” he said.
German ministers rebuffed the doubts of the Western military establishment. “We want to remain transatlantic but we also want to be more European,” said German defence minister Ursula von der Leyen. “Nato will always be collective defence but there are other tasks where Europe is needed.”
The tensions led Sigmar Gabriel, the German foreign minister, to lump the US with China and Russia as powers that “try to test and undermine the EU’s unity”.