Gregg Zoroya

USA TODAY

The president of Estonia quickly assured the world his nation, a 12-year member of NATO, is spending its fair share on defense. The Czech prime minister expressed hope the United States would not abandon his people in a crisis. A Latvian member of parliament worried about NATO disunity and broken promises.

They quickly reacted Thursday to Donald Trump's art-of-the-deal tough talk in an interview with The New York Times that NATO partners should pay their fair share of defense spending or risk abandonment by Washington if threatened with an attack.

Only five of NATO's 28 member-states meet their commitment of paying at least 2% of their economic output on defense, according to the alliance.

"We're talking about countries that are doing very well," the Republican presidential nominee told the Times. "Yes, I would be absolutely prepared to tell those countries, 'Congratulations, you will be defending yourself.'"

He said this would be his way of negotiating a financial commitment from allies in NATO and around the world.

"In a deal, you always have to be prepared to walk," Trump said in the interview. "Hillary Clinton has said, 'We will never, ever walk.' That's a wonderful phrase. But unfortunately, if I were on Saudi Arabia's side, Germany, Japan, South Korea and others, I would say, 'Oh, they're never leaving, so what do we have to pay them for?' Does that make sense?"

Trump appears to put conditions on aiding NATO allies

Article 5 of NATO's treaty says any attack on one member is an attack on all of them. The section has been invoked only once in the alliance's 66-year history and that was in response to the Sept. 11, 2001, terrorist attacks on the United States.

Estonia's President Toomas Hendrik Ilves tweeted Thursday that his nation had fought terrorism under Article 5 "with no caveats." He said, "We are equally committed to all our NATO allies, regardless of who they may be. That's what makes them allies."

The five NATO members who spend at least 2% of their economic output on defense are the United States, Greece, United Kingdom, Estonia and Poland.

Latvian lawmaker Ojars Kalnins, who chairs parliament's foreign affairs committee, told Latvian radio that Trump's remarks were "both dangerous and irresponsible."

"This won't be good for NATO unity or the security situation. In principle, he is saying the U.S. will not fulfill its promises or obligations." Kalnins said.

Trump's remarks come as Russian President Vladimir Putin has directed the largest military buildup by his country since the fall of the Soviet Union. His troops have overrun Ukraine's Crimea region and has supported separatists fighting the government in eastern Ukraine. Russian military aircraft and submarines operate provocatively close to NATO allies in eastern Europe.

"If Trump doubts NATO solidarity in the case of Article 5, then his election is dangerous for Baltic security," said Artis Pabriks, a former Latvian foreign and defense minister who is now a member of the European Parliament, on twitter.

Lithuanian President Dalia Grybauskaite expressed confidence that the United States would always stand by its allies. "We trust America," he said, Bloomberg reported.

"Whoever wins the presidential election, I hope the United States will remain a solid NATO partner," Czech Prime Minister Bohuslav Sobotka told reporters Thursday, according to Reuters.

The contretemps over Trump's NATO remarks brought an immediate response from his campaign. Indiana Gov. Mike Pence, the Republican vice presidential nominee, told Fox News that Trump would stand by America's allies, adding that he was simply urging nation's to "begin to carry the financial costs of these international obligations."

Trump campaign chairman Paul Manafort, in an interview with The Daily Beast, accused The New YorkTimes of misquoting the candidate. A transcript of the interview posted online by the Times showed the reporting was accurate.

American security analysts on both sides of the political spectrum roundly criticized Trump's remarks.

"I think the most charitable interpretation is he already sees himself engaged in negotiation with these (NATO allies) — that there hasn't been a fair burden-sharing," said John Hannah, a former adviser in George W. Bush White House and currently with the Foundation for Defense of Democracies.

"The only problem is that there are other audiences watching this as well," Hannah said. "To do that at a time of very high tension is overall a bad tactic. I don't think destroying NATO, whether it's because the allies are paying 2% or 1.5% is worth it."

Philip Gordon, a former Obama administration adviser now with the Council on Foreign Relations, suggested Trump's approach to NATO "seems to be to run it like a protection racket where if they don't pay up we're going to leave them to vulnerable attack."

"I think it crosses a new line," Gordon said. "You're telling the potential adversary, in this case Russia, that even a treaty obligation is something that our allies can't count on."