RAF FAIRFORD: Britain and Sweden agreed on Friday to study air combat co-operation and opened the door to other potential partners in a move that could see the Scandinavian country join a planned next-generation UK fighter project.

Britain last year unveiled plans for a fighter plane and cohort of drones named Tempest, raising questions about the future of European defence co-operation as France and Germany pursue their own air combat programme to meet growing threats.

Tempest, meant to eventually replace the Eurofighter Typhoon from 2040, will be developed and built by BAE Systems, Britain's biggest defence company, alongside UK engine maker Rolls-Royce, Italian defence firm Leonardo and European missile maker MBDA.

Sweden's Saab will not immediately join the same industrial team but will be involved in a broader technology study that sketches out Britain's post-Brexit defence partnerships and could lead to further countries coming on board, officials said.

"Brexit or not, Sweden has a strategic interest to further deepen its relations with the UK," Defence Minister Peter Hultqvist said at the Royal International Air Tattoo, a major military air show held in western England.

Britain's defence ministry said the agreement called for a joint combat air development and acquisition programme.

The study, which is expected to yield results by autumn 2020, "lays the foundations for collaboration and invites others to participate in our discussions," Britain's Defence Procurement Minister Stuart Andrew said.

Britain will remain a key partner for its European neighbours in NATO after leaving the European Union, he said.

Britain and Sweden have conducted joint exercises in the Baltic where Western officials say Russia has stepped up probing flights and mock bomb runs near Europe's borders since 2013.

European nations face a combination of security threats and budget constraints that have spurred competing alliances as Europe's fragmented defence industry vies for leadership and a slice of future spending on any new pan-European fighter.

Analysts say it is unclear whether Europe can afford more than one fighter programme in future rather than the current three - the French Rafale, Swedish Gripen and multinational Eurofighter, which includes Britain.

But defence analyst Francis Tusa said Britain and France had different military needs and that the amount of detailed work already undertaken by Britain and Sweden suggested the Tempest and Franco-German Future Combat Air System could both go ahead.