On 13 November 2017 ministers from 23 member states signed a joint notification on the Permanent Structured Cooperation (PESCO) and handed it over to the High Representative and the Council.

The possibility of the Permanent Structured Cooperation in the area of defence security and defence policy was introduced by the Lisbon Treaty. It foresees the possibility of a number of EU member states working more closely together in the area of security and defence. This permanent framework for defence cooperation will allow those member states willing and able to jointly develop defence capabilities, invest in shared projects, or enhance the operational readiness and contribution of their armed forces.

The member states who signed the joint notification are: Austria, Belgium, Bulgaria, Czech Republic, Croatia, Cyprus, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Latvia, Lithuania, Luxembourg, the Netherlands, Poland, Romania, Slovakia, Slovenia, Spain and Sweden. It is possible for other member states to join at a later stage.