CLEVELAND — Hours before he accepted the Republican presidential nomination Thursday, Donald Trump faced fierce international criticism for suggesting his administration might not defend NATO allies in Eastern Europe and may not speak out for human rights abroad.

A day that Trump's team had hoped would celebrate his improbable triumph in the GOP instead shifted to concerns he would upend a network of U.S. security guarantees put in place after World War II and embraced or expanded by every president since.

Trump's comments in an interview with The New York Times drew a swift and furious reaction from foreign diplomats as well as the GOP foreign policy establishment.

NATO indirectly rebuked Trump for suggesting the U.S. might not defend a member state under attack, a growing concern for NATO members Poland, the three Baltic states and others fearful of Russian aggression since its 2014 incursion in Ukraine.

In a statement from Brussels, the 70-year-old organization said solidarity was a “key value” of the 28-nation military alliance and noted that troops from its members had served alongside U.S. forces in Afghanistan and elsewhere.

In recent months, Trump has repeatedly kicked at cornerstones of U.S. foreign policy. Many of his recent critiques have centered on whether alliances credited with maintaining peace in postwar Europe and containing a bellicose North Korea are too expensive.

He went further in the latest interview, however.

Asked whether the three tiny Baltic nations — Latvia, Lithuania and Estonia — and other NATO allies could count on the U.S. pledge to defend them if Russia attacks, Trump said it would depend on whether the country had met its financial obligations.

“Have they fulfilled their obligations to us?” he said. “If they fulfill their obligations to us, the answer is yes.”

He was reluctant to criticize mass arrests of judges, teachers, military officers and others by Turkish President Recep Tayyip Erdogan since last week's failed coup attempt.

The European Union and Secretary of State John Kerry have urged Turkey to honor the rule of law and democratic values, but Trump suggested that such advice, coming from America, was out of line.

“Right now when it comes to civil liberties, our country has a lot of problems, and I think it's very hard for us to get involved in other countries when we don't know what we are doing and we can't see straight in our own country,” he told the newspaper.

Trump also questioned anew whether U.S. troops should be deployed in South Korea and Japan to deter the North Korean threat and to counter China's regional expansion in the South China Sea.

Trump's campaign manager, Paul Manafort, initially suggested he had been misquoted, but a transcript released by the newspaper matched quotations attributed to the candidate.

His son Eric Trump then mounted a staunch defense, but he left it unclear whether his father might break treaty commitments to allies that fail to pay their share for defense.

“Right now, we subsidize the vast majority of NATO — how is that fair?” he told CBS News. “You have countries that are part of NATO and who don't pay anything or pay very, very little.”

The foreign policy flap drew a scathing rebuke from the campaign of Hillary Clinton, Trump's Democratic rival.

“It is fair to assume that Vladimir Putin is rooting for a Trump presidency,” said Jake Sullivan, a senior Clinton policy adviser. He suggested Trump has “a bizarre and occasionally obsequious fascination with Russia's strongman.”

Senate Majority Leader Mitch McConnell of Kentucky was more forgiving. “I am willing to kind of chalk it up to a rookie mistake,” he tweeted.

Policy experts from across the political spectrum were flummoxed by Trump's comments.

“Mr. Trump clearly doesn't understand what the word ‘treaty' means, because a treaty means you have an obligation to those countries,” said Danielle Pletka, a senior vice president at the American Enterprise Institute, a conservative think tank.

Retired Gen. Wesley Clark said Trump's stance “undercuts NATO's deterrent in Europe” and showed a fundamental misunderstanding of NATO.

Some foreign policy experts branded Trump's comments as an attempt, in effect, to monetize American defense obligations.

“Trump sees alliances as revenue-generating service,” tweeted Vali Nasr, dean of Johns Hopkins University's School of Advanced International Studies. Trump was turning U.S. foreign policy “on its head,” he wrote.

Daniel Drezner, a professor of international politics at Tufts University, sarcastically posited that Trump could be right that the Korean peninsula might well be unified if not for the presence of U.S. troops — unified, he said, under control of the North. “If you know anything about foreign policy, you can't read that interview and not be terrified,” Drezner said.

The controversy comes days after Trump's surrogates reportedly intervened to help rewrite a portion of the GOP platform in Cleveland to eliminate references to arming Ukraine in its fight with Russia.

Manafort, Trump's campaign manager, had worked as a campaign consultant for the now-ousted pro-Moscow president in Ukraine before Russia seized the Crimean peninsula in 2014 and provided support for armed separatists in eastern Ukraine.

Manafort was asked about the GOP position in Ukraine at a press conference in Cleveland, but he deflected the question, saying only that the world needs a “strong U.S. presence.”

Los Angeles Times' Michael Finnegan contributed from Cleveland.

laura.king@latimes.com