Donald Trump Sets Conditions for Defending NATO Allies Against Attack

CLEVELAND — Donald J. Trump, on the eve of accepting the Republican nomination for president, said Wednesday that if he were elected, he would not pressure Turkey or other authoritarian allies about conducting purges of their political adversaries or cracking down on civil liberties. The United States, he said, has to “fix our own mess” before trying to alter the behavior of other nations.

“I don’t think we have a right to lecture,” Mr. Trump said in a wide-ranging interview in his suite in a downtown hotel here while keeping an eye on television broadcasts from the Republican National Convention. “Look at what is happening in our country,” he said. “How are we going to lecture when people are shooting policemen in cold blood?”

During a 45-minute conversation, he explicitly raised new questions about his commitment to automatically defend NATO allies if they are attacked, saying he would first look at their contributions to the alliance. Mr. Trump re-emphasized the hard-line nationalist approach that has marked his improbable candidacy, describing how he would force allies to shoulder defense costs that the United States has borne for decades, cancel longstanding treaties he views as unfavorable, and redefine what it means to be a partner of the United States.

He said the rest of the world would learn to adjust to his approach. “I would prefer to be able to continue” existing agreements, he said, but only if allies stopped taking advantage of what he called an era of American largess that was no longer affordable.

Giving a preview of his address to the convention on Thursday night, he said that he would press the theme of “America First,” his rallying cry for the past four months, and that he was prepared to scrap the North American Free Trade Agreement with Mexico and Canada if he could not negotiate radically better terms.

He even called into question whether, as president, he would automatically extend the security guarantees that give the 28 members of NATO the assurance that the full force of the United States military has their back.

For example, asked about Russia’s threatening activities that have unnerved the small Baltic States that are among the more recent entrants into NATO, Mr. Trump said that if Russia attacked them, he would decide whether to come to their aid only after reviewing whether those nations “have fulfilled their obligations to us.”