Defense Secretary Ash Carter chided America's European allies on Wednesday, saying a long slide in European defense spending calls into question its ability to partner with the U.S. military at a time of growing security threats across Europe.

"They're not doing enough," Carter said in an unusually blunt assessment of the Europeans' defense efforts. He said they are spending a smaller share of their overall economic wealth on defense than they did in the past.

"It's too low," he said. "And if Europe wants to be a force in the world it needs to be more than a moral and political and economic force, which Europe is because it shares many of our values and demonstrates them around the world. But it has to have the military power that goes with that as well.

"It has to have the military power to be a capable ally of ours, and we see that slipping. It has got to turn around. It's not that they don't have the money to do it."

Carter made his comments in response to a question from his audience at Georgetown University after delivering a speech about eradicating sexual assault from the military and providing help for assault victims.

Carter has not visited Europe since taking office in February. He is expected to attend his first meeting of NATO defense ministers in Brussels in June.

He noted that at the alliance's meeting last September in Wales the leaders agreed to reverse the trend of declining defense budgets and to spend more wisely. They agreed that any NATO member not spending at least 2 percent of its gross domestic product on defense will "aim to move toward" that goal within a decade.

U.S. defense secretaries have long complained that the Europeans spend too little on their own defense but they usually are not as blunt about it as Carter.

"They've got the money to do this," he said, adding that when the Cold War ended in 1990 -- and with it the threat of invasion or attack by the Soviet Union and its Warsaw Pact allies -- U.S. allies in Europe concluded that their security problems were over.

"Now they're beginning to wake up," he said, referring to such recent security crises as the Russian military intervention in eastern Ukraine, the January terrorist attack on the Paris office of the Charlie Hebdo satirical newspaper, and Turkey's proximity to the Islamic State violence in Iraq and Syria.

"So it's not like they (the Europeans) don't have plenty to do," Carter said. "And it's not like we have to do everything ourselves."

Carter acknowledged that the Obama administration faces its own challenges on the military spending front. He reiterated a plea for Congress to avoid the across-the-board defense spending cuts known as sequestration in 2016.

"Sequestration is a sudden and arbitrary cut in the defense budget that we can't predict," he said. The effect thus far, he added, has been to compensate by taking money from military training budgets and weapons development projects -- "in short, doing all kinds of stupid things."

"This idea that you can skimp when the world is as tumultuous as it is ... is false."