"I will expect the next Foreign Affairs Council to adopt this formal decision, so that we will be able to launch for the first time ever a European Defense Permanent Structured Cooperation with concrete projects, announced EU Foreign Policy Chief Frederica Mogherini".
Apart from Britain, Denmark, Portugal, Ireland and Malta have yet to decide whether to join the pact.
Twenty-three countries have declared they will participate in a new EU defense cooperation pact, part of a broader push to advance European integration, officials said Monday. The EU stresses that PESCO is complimentary to North Atlantic Treaty Organisation, in which 22 of the EU's 28 countries are members.
The European Council has agreed in June to establish PESCO and the EU leaders discussed the progress in preparing during last summit.
"The real problem is not how much we spend, it is the fact that we spend in a fragmented manner", Mogherini said.
European Union foreign and defense ministers from 23 of the 28 member countries, signed a landmark defense agreement Monday in Brussels aimed to boost post-Brexit cooperation within the bloc and to counter Russian pressure.
European Union officials insist this is not just bureaucratic cooperation, but real investment that will help develop Europe's defense industry and spur research and development in military capabilities that the bloc needs most.
"We are agreeing on the future cooperation on security and defence issues ... it's really a milestone in European development", he added.
This has led to unease by European allies that the US was not committed to the alliance's mutual defense pact. The EU, she said, has tools to fight hybrid warfare - the use of conventional weapons mixed with things like propaganda and cyber-attacks - that the American-led military alliance does not have at its disposal.
The notification letter - co-authored by France, Germany, Italy, and Spain - described the pact as "an ambitious, binding, and inclusive European legal framework for investment in the security and defense of the EU's territory and its citizens". At launch the focus will be project-driven such as the development new military equipment such as tanks or drones.
The agreement commits countries to "regularly increasing defence budgets in real terms" as well as devoting 20 per cent of defence spending to procurement and 2 per cent to research and technology.