Defense Secretary Ash Carter is calling on Europe to spend more on defense in light of security threats like terrorism and Russia's intervention in Ukraine.

Carter made the plea Wednesday during a question-and-answer sessions with Reserve Officer Training Corps cadets at Georgetown University.

Carter said that if Europe wants to play its proper role as a U.S. ally it needs to boost its defense budgets. He said the U.S. sees the Europeans' defense capabilities "slipping," even though they could afford to spend more.

Carter also made a plea for Congress to avoid the across-the-board defense spending cuts known as sequestration in 2016.