BRUSSELS — Foreign and defense ministers of European Union members reached a deal on Monday to create a headquarters for military training operations — setting aside, at least for now, concerns that the step might lead to the establishment of a “European army” to rival NATO.

France and Germany support the proposal and have pressed the European Union to do more to ensure its own defense and counter the threat of terrorism.

Britain has long opposed anything that resembled a European military command — but it has voted to leave the European Union, and that has altered the dynamic of the debate. With the United States appearing to take a step back in its role in the world, the core pair of France and Germany is pushing the European Union to take greater responsibility for its security.

The European Union and NATO have overlapping memberships: Of the 28 nations in the European Union, all but six — Austria, Cyprus, Finland, Ireland, Malta and Sweden — also belong to NATO. Albania, Iceland, Norway and Turkey are in NATO but are not part of the European Union, as are Canada and the United States.