Ursula Von der Leyen said Europe “needs to improve its ability to act on behalf of its own security” at a time of global uncertainty, adding major progress has been made towards realising a joint defence force.
Like the development of the EU’s single market and free movement principle, developing a European army will take time, she said.
But she said cooperation between member states has been boosted in recent months thanks to new reforms and the “obvious benefit” of working together.
Writing in the German newspaper Handelsblatt, Ms Von der Leyen hit back at claims by another German politician who argued the EU should forge ahead with building a “real European army” instead of just talking about it.
In response, she said Wolfgang Clement was right in principle but had neglected to mention “the progress we Europeans have made in the last few years”.
She said: “Europe’s army is already taking shape.
“Reforms over the past months and years have brought our armed forces closer together. We’re working quickly.
“But let’s not forget that achievements that are now taken for granted, such as the internal EU market or freedom of movement didn’t happen overnight.
“They came about thanks to careful, measured progress, and member states pursing clear goals, one step after another.”
EU leaders including Angela Merkel and Emmanuel Macron have previously expressed their hopes of forming an EU defence force.
Speaking in November, the French leader said a “true European army” is required to protect the interests of the bloc as the United States under President Donald Trump continues to look inward.
His vision was backed by Ms Merkel who said she supported a “real, true” European army.
But the prospect of an EU army has received fierce criticism from British Defence Secretary Gavin Williamson, who warned any force which rivaled NATO would undermine international security.
Branding the plan “crazy and dangerous”, Mr Williamson vowed Britain would “never” be part of the project.
He went on to condemn the majority of EU member states who had failed to hit the NATO military spending target of two percent of GDP – a list which includes France and Germany.
Twenty-five EU members have already pledged to combine their military forces on a regular basis through the Permanent Structured Cooperation (PESCO) pact.
Launched in late 2017, the agreement already involves projects including the formation of the EUFOR Crisis Response Operation Core which some see as a precursor to a fully fledged EU army.
Britain is not part of PESCO but will be able to take part in projects on “third country” terms if it chooses.