13 September, 2017
In the paper, which will be published today (September 12) the Government underlines its substantial defence budget, the seat on the UN Security Council, nuclear weapons and troops being deployed in Eastern Europe.
The negotiations are now likely to start on September 25, two of the officials said.
Britain has deployed troops in some Baltic states to counter a resurgent Russian Federation, has worked with the European Union to tackle piracy off the Horn of Africa and worked on joint defence projects, such as the Eurofighter Typhoon aircraft.
Britain's role in the continent's defence "has never been more vital", he said.
Another source said Britain asked for the delay to let May set out London's latest views and plans on Brexit before more negotiations.
Foreign secretary Boris Johnson said the government envisaged a strong UK-EU partnership on foreign and defence policy after the UK's withdrawal. "It's in our mutual interest to work closely with the European Union and its member states to challenge terrorism and extremism, illegal migration, cyber-crime, and conventional state-based military aggression".
Tuesday's paper was intended as a conversation-starter rather than a concrete negotiating position, setting out areas such as information and personnel exchanges where Britain could contribute to European security, subject to negotiations.
British officials have long championed defence cooperation with European nations, with some suggesting it could be used as leverage in talks which so far have moved slowly, bogged down in arguments over the divorce bill.
It also poses a "major threat" to Britain's place in the Five Eyes intelligence co-operative with Australia, New Zealand, Canada, and the United States - since its Anglosphere partners are reluctant to be over-exposed to the EU's often leaky and unreliable security agencies.
James Walsh, of the Pensions & Lifetime Savings Association, a trade body, said: "The UK and European Union have agreed that the UK will continue paying and uprating state pensions to UK citizens living in European Union countries after Brexit - and vice versa".