[akvadrako]

Even if not exactly joining NATO, there is an attempt to create close military ties:

The Common Security and Defence Policy (CSDP): "Berlin plus agreement" from March 2003, which allows the EU to use NATO structures, mechanisms and assets to carry out military operations if NATO declines to act.

The European Defence Agency (EDA): established in July 2004 and is based in Brussels. It supports the EU Member States in improving their military capabilities in order to complete CSDP targets as set out in the European Security Strategy.

The European Union–Ukraine Association Agreement (EUUAA): The agreement commits both parties to promote a gradual convergence toward the EU's Common Security and Defence Policy (CSDP) and European Defence Agency (EDA) policies.