Donald Trump gestures during the first presidential debate, at Hofstra University in Hempstead, N.Y. (AFP/Getty Images)

BRUSSELS — Republican nominee Donald Trump said during Monday's presidential debate that he was "all for NATO,” a shift that was likely to offer a mix of relief and confusion to U.S. military allies around the world.

In doing so, Trump backed down from his suggestion over the summer that he would check whether U.S. allies "fulfilled their obligation to us" before coming to their defense — stressing financial obligations.

That assertion upended decades of U.S. military doctrine, unsettling allies who count on American guarantees of their security, particularly in Eastern Europe, which is fearful of Russia.

Trump said during the debate with Democratic nominee Hillary Clinton that he now supports NATO because it has listened to him by moving into terrorism. That is false, NATO has previously said — a plan to create a new intelligence director was underway long before Trump started surging in the polls — but it was apparently enough for Trump.

"I'm all for NATO,” Trump said at the debate, “but I said they have to focus on terror, also. And they're going to do that. And that was, believe me, not going to get credit for it, but that was largely because of what I was saying and my criticism of NATO.”

The NATO plans were announced before the July 20 Trump interview with the New York Times in which he questioned U.S. commitments to the alliance.

Trump's shifting positions have left U.S. allies concerned but with little recourse to make plans if he is elected. NATO plans to deploy multinational battalions to the four alliance countries that border Russia early next year. The United States is taking the lead on the deployment in Poland.

NATO countries can’t plan for Trump “because his position keeps shifting,” a senior NATO diplomat said ahead of the debate, speaking on the condition of anonymity to discuss internal NATO talks. NATO’s most vulnerable countries are waiting to see whether U.S. policy actually changes if Trump is elected, the diplomat said.

The U.S. spends more than 2½ times as much on defense as the other NATO nations combined, which has long been a sore point for both Democratic and Republican policymakers who say Europe relies too much on the United States for its defense. Just five of NATO’s 28 nations spend more than the alliance’s recommended level of 2 percent of GDP on defense.

E.U. nations have begun talks about increasing defense cooperation, a move that comes partly as a reaction to U.S. pressure and partly because of the British vote to leave the European Union.

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