Donald Trump told The New York Times that if elected, he would not automatically come to the aid of NATO allies in the Baltics if they came under Russian attack.
In the interview Wednesday, he also said he would not pressure Turkey about purges or crackdowns on civil liberties following the failed coup last weekend.
Claiming that the U.S. has to "fix our own mess" before intervening in the running of other countries, Trump told the Times he would press the hard-line nationalist "America First" theme of his campaign.
"I don't think we have a right to lecture," Trump told the newspaper ahead of his address Thursday night acceptance speech at the Republican National Convention. "Look at what is happening in our country. How are we going to lecture when people are shooting policemen in cold blood?"
Trump added that, if elected, the U.S. would not automatically guarantee security to the 28 members of NATO. Russia recently started a review of the terms of Baltic countries' independence from the former Soviet Union in 1991.
The GOP presidential candidate told the Times he would decide to go to the aid of small Baltic states only once he reviewed whether they had "fulfilled their obligations to us."
He added, "If they fulfill their obligations to us, the answer is yes."
At a press conference in Vilnius, Lithuanian President Dalia Grybauskaite told journalists: "Regardless of who becomes the next president of the United States, we trust America. It has always defended nations under attack, and will do so in the future."
A spokesman for the Estonian prime minister said: "Estonia's commitment to our NATO obligations is beyond doubt, and so should be the commitments by others."