(CNN) Donald Trump, in a New York Times interview published Thursday, outlined a sharp break in US foreign policy tradition, suggesting the US wouldn't defend NATO allies like the Baltic states against Russian aggression if they haven't "fulfilled their obligation to us."
Trump has repeatedly made the case that most of NATO's 28-member countries are not making the requisite financial contributions for their common defense, and he's said in the past that "the US must be prepared to let these countries defend themselves."
Throughout the interview, the Republican presidential nominee seemed to reject core assumptions of US military and foreign policy thinking -- including foreign troop deployment and advocating for civil liberties -- and argued for an unprecedented global retrenchment, frequently framing his argument in economic terms.
Trump's comments were met with shock and anger in some quarters, drawing stern rebukes from members of both parties and prompting the White House to assuage anxious allies. They also made matters awkward for Trump's vice presidential choice, Mike Pence, who delivered a speech at the Republican National Convention within hours of the interview being posted online that contrasted in places with his running mate.
At one point, Pence told the RNC audience that Trump would "stand with our allies."
"We cannot have four more years of apologizing to our enemies and abandoning our friends," Pence said.
Though Trump said, "I would prefer to be able to continue" existing international agreements, he later explained that "this is not 40 years ago." He also suggested that the massive expense of maintaining an international order that is contributing to trade losses for the US "doesn't sound very smart to me."
"We are spending a fortune on a military in order to lose $800 billion," Trump said.
Trump questioned the forward deployment of American troops when answering a question about the tension in the South China Sea. According to the Times interview, Trump explained that "it will be a lot less expensive" for the United States to deploy military assets domestically.
Trump was also asked about the recent attempted coup in Turkey, praising President Recep Erdogan "for being able to turn that around."
And Trump suggested that the US shouldn't chide Erdogan's administration about potential violations of civil liberties because "when the world sees how bad the United States is and we start talking about civil liberties, I don't think we are a very good messenger."
"I don't think we have the right to lecture," he said.
NATO secretary general Jens Stoltenberg, in an unusual statement about American domestic politics, responded to Trump's comments with a call for solidarity.
"I will not interfere in the US election campaign, but what I can do is say what matters for NATO," Stoltenberg said in a statement to CNN. "Solidarity among Allies is a key value for NATO. This is good for European security and good for US security. We defend one another."
Toomas Hendrik, president of NATO member Estonia, appeared to respond to Trump's comments on Twitter, though he didn't mention the GOP nominee by name.
"Estonia is (one) of 5 NATO allies in Europe to meet its 2% def expenditures commitment," Hendrik tweeted. "Fought, with no caveats, in NATO's sole Art. 5 op. in Afg."
White House Press Secretary Josh Earnest said Thursday that the United States' commitment to the mutual defense pact is "ironclad."
"This is a longstanding commitment that has been strengthened under the leadership of President Obama," Earnest said. "There should be no mistake or miscalculation made about this country's commitment to our country's transatlantic alliance."
Hillary Clinton's campaign put out a statement early Thursday morning following the publication of Trump's interview, slamming his remarks and saying, "It is fair to assume that Vladimir Putin is rooting for a Trump presidency."
"For decades, the United States has given an ironclad guarantee to our NATO allies: we will come to their defense if they are attacked, just as they came to our defense after 9/11. Donald Trump was asked if he would honor that guarantee. He said... maybe, maybe not," Clinton said.
The former secretary of state continued, "Ronald Reagan would be ashamed. Harry Truman would be ashamed. Republicans, Democrats and Independents who help build NATO into the most successful military alliance in history would all come to the same conclusion: Donald Trump is temperamentally unfit and fundamentally ill-prepared to be our Commander in Chief."
Sen. Tim Kaine of Virginia, who has been pegged as a possible Clinton running mate, said he was "stunned" by Trump's remarks.
"When you say to an ally who you have a treaty obligation to defend, 'Eh, we're not sure we will,' that's a very dangerous thing," Kaine said at a press conference on Thursday.
Sen. Lindsey Grahham, a South Carolina Republican who challenged Trump in the Republican primaries, also denounced the GOP nominee's comments.
"Statements like these make the world more dangerous and the United States less safe," Graham said in a statement. "The Republican nominee for President is essentially telling the Russians and other bad actors that the United States is not fully committed to supporting the NATO alliance."
Graham, who last month urged Republicans to rescind their endorsements of the nominee, said he hopes Trump will "correct" his remarks in his speech at the Republican National Convention on Thursday night.
Sen. Tom Cotton, an Arkansas Republican who is publicly supporting Trump and who spoke at the RNC earlier this week, differed with Trump's NATO comments Thursday.
He told CNN's Jake Tapper that the US is in the trans-Atlantic military alliance "because it's in our national security interest."
"We want to strengthen NATO and strengthen our common defenses," he said. "Another part of strengthening it is making clear we're going to stand by our security pledge."
Not doing so, he continued, "doesn't make it less likely to get into a hot war, it ultimately makes it more likely."
In an interview with Fox News on Thursday morning, Pence said he hadn't seen "the exact context" of the comments on NATO, but the Indiana governor nevertheless didn't take issue with Trump's position.
"I think Donald Trump's position very broadly with regard to our allies and with regard to treaty obligations and NATO is that it's time for our allies to begin to pay their fair share. It's time for people to begin to step up," Pence said.
He added, "The NATO alliance since World War II has been a mutual defense alliance and I have every confidence that Donald Trump will see to it that the United States of America stands by the allies and lives up to the treaty obligation."
Trump also found a sympathetic ear in Nigel Farage, the former leader of the UK's Independence Party and one of the most vocal supporters of Britain's decision to leave the European Union.
"I think the American military over the last few years has been pretty unhappy with their NATO allies, who have just kept cutting, cutting, cutting their defense spending," Farage said, adding that NATO was "a wonderful vehicle to keep peace in Europe for 60, 70 years."
"But NATO now does need to redefine itself," he said. "What is it for? We don't have the Warsaw Pact. I'm pro-NATO. I'm pro-cooperation. But it's not a bad thing that we reassess what it's for."