Attendees pose for group photos after signing a pact on joint defense cooperation at the headquarters of the European Council in Brussels, Belgium, Nov. 13, 2017. (Xinhua/European Union)

BRUSSELS, Dec. 11 (Xinhua) -- The Council of the European Union on Monday adopted a decision establishing the Permanent Structured Cooperation (PESCO), with 25 participating EU member states.

PESCO is an instrument in the EU treaty to enable willing member states to pursue greater cooperation in defense and security.

This framework allows EU member states to jointly develop defense capabilities, invest in shared projects, or enhance the operational readiness and contribution of their armed forces.

In November, defense ministers of 23 EU member states signed a joint notification on PESCO and handed it over to EU foreign policy chief Federica Mogherini. Britain, Denmark, Portugal, Ireland and Malta have yet to decide whether to join the pact.

According to a statement released by the Council of the EU Monday, Ireland and Portugal also notified their decision to join PESCO last week.

The Council decision sets out an initial list of 17 projects to be undertaken under PESCO.

The European Commission welcomed the decision adopted by the Council formally establishing PESCO and the plans to establish 17 projects on defense by 25 countries.

European Commission President Jean-Claude Juncker said: "I welcome the steps taken today by member states to lay the foundations of a European Defense Union. Europe cannot and should not outsource our security and defense."