President Obama on Wednesday expressed concern that NATO members were not spending enough on defense, saying it was important to ensure that all of the alliance’s members were “chipping in.”

“If we’ve got collective defense, it means that everybody’s got to chip in. And I have had some concerns about a diminished level of defense spending among some of our partners in NATO; not all, but many,” Obama warned during a joint press conference at the Council of the European Union in Brussels.