WASHINGTON — Republican nominee Donald Trump hinted the U.S. may revisit NATO’s longstanding policy of defending its allies against possible Russian aggression if he becomes president, saying that some allies aren’t holding up their end of the bargain.

Trump told The New York Times that he would decide whether to protect the Baltic republics against any incursion by Russia based on whether those countries “have fulfilled their obligations to us.”

His remarks came ahead of his speech to formally accept the Republican nomination for president late Thursday, and dominated the day’s convention-related chatter, even though they are in in line with his views questioning the United States’ global role.

In 2014, the 28-member alliance created a rapid-reaction force to protect the most vulnerable NATO members against a confrontation with Russia. Last week, President Barack Obama pledged unwavering commitment to defending Europe, adding that “in good times and in bad, Europe can count on the United States.”

White House spokesman Josh Earnest reaffirmed the United States’ commitment to its trans-Atlantic partners.

“The cornerstone of that alliance is the pledge that all of the allies have made to mutual self-defense,” Earnest said. “The U.S. commitment to that pledge is iron-clad,” Earnest said.

NATO, or the North Atlantic Treaty Organization, is a military alliance of European and North American democracies created after World War II to strengthen international cooperation as a counter-balance to the rise of the Soviet Union.

NATO Secretary-General Jens Stoltenbert said he wouldn’t wade into the U.S. presidential campaign, but he noted that “solidarity among allies is a key value for NATO.”

“This is good for European security and good for U.S. security. We defend one another. We have seen this in Afghanistan, where tens of thousands of European, Canadian and partner nation troops have stood shoulder-to-shoulder with U.S. soldiers.”

Presumptive Democratic nominee Hillary Clinton’s campaign was quick to pounce on Trump’s statements.

“The president is supposed to be the leader of the free world. Donald Trump apparently doesn’t even believe in the free world,” Clinton senior policy adviser Jake Sullivan said in a statement shortly after the interview was published.

Trump’s running mate, Indiana Gov. Mike Pence, was on the defensive early Thursday, telling Fox News he is confident the Republican nominee would stand by America’s NATO allies. But he insisted those countries “must pay their fair share.”

Pence added that a Trump administration would tell U.S. allies “the time has come for them and for their citizens to begin to carry the financial costs of these international obligations.”

Trump has publicly welcomed praise from Russian President Vladimir Putin, telling MSNBC in December that, “when people call you brilliant, that’s always good, especially when the person heads up Russia.” When the interviewer pointed out charges that Putin kills opponents and that he invaded neighboring Ukraine, Trump responded that Putin is “running his country, and at least he’s a leader, unlike what we have in this country.”

Republican Sen. Lindsey Graham, an outspoken Trump critic, said Thursday that Trump’s statements make Putin “a very happy man.”

“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 said.

Even Putin’s spokesman, Dmitry Peskov, took issue with part of Trump’s remarks, saying that “the phrase about Russia even hypothetically attacking someone is unfortunate wording.”

Trump also told The Times that he would not criticize Turkey for cracking down on political opponents and restricting civil liberties following last week’s attempted coup. Of Turkish President Recep Tayyip Erdogan, Trump said: “I give great credit to him for being able to turn that around.”

The U.S. has no “right to lecture” Turkey and other countries when “people are shooting policemen in cold blood,” Trump said.

With decades in business and no prior political experience, Trump cast the projection of American military might abroad in economic terms.

For example, he said it might not be necessary to station American troops abroad, though he agreed it’s preferable.

“If we decide we have to defend the United States, we can always deploy” troops from the U.S., Trump told the newspaper, “and it will be a lot less expensive.”