A group of European Union countries agreed yesterday to develop their first joint defense projects under a pact that excludes Britain, giving London a taste of life outside the bloc's foreign policy decision-making process.

The 25 signatories to the pact also delayed a decision on whether to let non-member states join the projects, prolonging uncertainty over any future role for Britain after it leaves the EU next year.

As Europe's biggest military power along with France, Britain is central to European security efforts but has long blocked defense integration, fearing the creation of an EU army.

Nevertheless, Britain is concerned about being left outside the new cooperation pact and missing out on weapons projects. Prime Minister Theresa May wants to reach a "security treaty" with the EU by 2019. Defense ministers from the pact's signatory states, which comprise all but three of the current EU members, signed off in Brussels on 17 collaborative projects. These include a European armored infantry fighting vehicle, underwater anti-mine sensors and a European medical command.

The eventual aim of the Permanent Structured Cooperation pact is to develop and deploy forces together, backed by a multi-billion-euro fund for defense research and development that is now under negotiation.

One senior EU official said ministers want to see more progress in Britain's exit negotiations with Brussels given the sensitive nature of defense cooperation with London.