BRUSSELS — The European Union must do more in the defense field, starting with creation of an EU military headquarters and working toward a common military force, the head of the EU’s executive arm said Wednesday, insisting the bloc’s economic and cultural influence isn’t enough to safeguard its place in today’s uncertain world.

Jean-Claude Juncker, EU Commission president, said in a major speech that the 28-nation organization “should be stronger” militarily.

“Together we have to make sure that we protect our interests,” Juncker told the European Parliament in Strasbourg, France.

The EU leader stressed that the bloc’s actions should take place in concert with the U.S.-led NATO defense alliance, to which 22 EU member states also belong.

“More European defense in Europe doesn’t mean less trans-Atlantic solidarity,” Juncker said.

The decision in June by British voters to withdraw from the European Union would deprive the EU of its militarily most capable member. France and Germany, the bloc’s two most influential member states, recently submitted a proposal for greater EU defense coordination, ranging from creation of a logistics hub for pooling military transport to an EU military headquarters.

Earlier this year, U.S. President Barack Obama called on Europeans to do more in meeting common security threats like the Islamic State extremist group.

“We need a strong Europe to bear its share of the burden, working with us on behalf of our collective security,” Obama said in Hannover, Germany, in April.

Obama added: “I’ll be honest, sometimes Europe has been complacent about its own defense.”

In the face of a more bellicose Russia, violent Islamic extremism, cyberattacks and other modern challenges, NATO and EU officials say they now collaborate more closely than ever. But NATO Secretary-General Jens Stoltenberg cautioned earlier this month that “the thing we have to avoid is duplication.”

The EU’s Lisbon Treaty, which took effect in 2009, foresaw a mechanism for permanent defense cooperation inside the bloc, but squabbles among member states have prevented the topic from even being broached at meetings of EU leaders, said Marcin Terlikowski, a European security expert at the Polish Institute of International Affairs.

If Juncker’s proposals are enacted, “it truly will be a quantum leap in EU defense cooperation,” Terlikowski said. He said some early reality checks will come at the Sept. 26-27 meeting of EU defense ministers, and a summit of bloc leaders scheduled for December.

Juncker’s proposals, made during his annual “State of the European Union” address, got a mixed reception at the European Parliament.

“We need a European Defense Union — for our internal and external security,” said liberal leader Guy Verhofstadt, a former Belgian prime minister. “The Americans want us to take more responsibility for our neighborhood. We need credible, hard power ourselves.”

British Conservative lawmaker Syed Kamall in contrast accused Juncker of indulging in the kind of “supranationalism” that turned so many Britons against the bloc.

Juncker said greater defense cooperation also makes economic sense for EU member nations, since it would reduce as much as 100 billion euros’ worth of wasteful duplication of spending yearly. By the end of 2016, he said, he will seek creation of a European defense fund to help spur military-related research and development.