VILNIUS (Reuters) - Germany’s defense minister called for a European “defense union” on Thursday during a visit to the Baltic state of Lithuania, where Berlin is preparing to lead a battle group of about 1,000 troops as a deterrence against neighboring Russia.

German Defence Minister Ursula von der Leyen arrives for a cabinet meeting at the Chancellery in Berlin, Germany August 24, 2016. REUTERS/Stefanie Loos

The European Union has long considered forging closer defense ties while not undermining the U.S.-led NATO alliance, to which many EU member states also belong, especially in the face of a more aggressive Russia and worsening conflicts in the Middle East.

The decision of Britain, a staunch opponent of any EU “army”, to quit the EU has also removed an obstacle to the closer European defense cooperation favored by Germany, France and many eastern European countries.

“It’s time to move forward to a European defense union, which is basically a ‘Schengen of defense’,”, Ursula von der Leyen told reporters in the Lithuanian capital Vilnius.

“That is what the Americans expect us to do.”

Schengen refers to the passport-free zone covering much of Europe, a pillar of the more integrated Europe that Germany strongly supports.

German Chancellor Angela Merkel also recently endorsed the idea of more joint military operations with the three Baltic republics, all NATO and EU members which have felt especially vulnerable following Russia’s annexation of Ukraine’s Crimea peninsula and its support for separatists in eastern Ukraine.

Germany already has close military ties and joint forces with Poland, the Netherlands and France outside NATO structures, though Berlin and Paris also say they do not envisage establishing a European army.

“When we have threats that are surrounding us, we all know no country by its own will be able to manage that. But we together, we Europeans, we are very strong if we improve our capabilities as Europeans,” von der Leyen said.

The German-led battle group in Lithuania will operate air defenses when it is deployed early next year, she added.

“There will be a comprehensive air defense”, she said. “We are very glad that we find many European friends who want to join, like the Dutch or the French, for example.”

NATO leaders agreed in July to move four battalions totaling 3,000 to 4,000 troops to the Baltic states and eastern Poland for the first time and to increase air and sea patrols to reassure those countries following Russia’s seizure of Crimea.