Donald Trump has cast further doubt on American international relations should he be elected president by suggesting that the US may not automatically defend Nato allies if attacked.
Mr Trump's remarks in an interview with the New York Times, published late on Wednesday, mark an escalation of his negative view of the country's military alliances with foreign countries.
The comments suggest a new, isolationist American foreign policy in an increasingly volatile world should he win the Oval Office on November 8th.
Speaking ahead of his acceptance speech for the Republican presidential nomination on the final day of the party’s convention in Cleveland on Thursday night, Mr Trump presented a foreign policy that would push the US to “fix our own mess” before intervening to help other countries.
The property and entertainment mogul, formally chosen as the Republican presidential nominee on Tuesday night, framed his proposed shift in US foreign policy in economic terms, reiterating his intentions to force US allies to contribute more financially to Nato.
Asked about a threat of Russian expansionism that is alarming new Nato members, Mr Trump said that as president he would come to the aid of Baltic states if they were attacked by Moscow only after reviewing whether those countries “have fulfilled their obligation to us”.
Offering an apparent preview of his speech to the convention on Thursday night on the “America First” theme of his presidential campaign, Mr Trump acknowledged that his foreign policy was a radical departure from the traditional interventionist approach of the
He renewed his threat to withdraw US troops deployed around the world in response to what he said were US trade losses. “We are spending a fortune on military in order to lose $800 billion – that doesn’t sound very smart to me.”
Presumptive Democratic nominee Hillary Clinton's campaign criticised Mr Trump, saying Republican favourite Ronald Reagan "would be ashamed" by the billionaire's undermining of the decades-long "ironclad guarantee" to Nato allies.
"Donald Trump was asked if he would honour that guarantee. He said . . . maybe, maybe not," said Mrs Clinton's senior policy adviser, Jake Sullivan.
Mr Trump's published remarks sparked alarm, raising warnings that they might embolden Russia.
"Solidarity among allies is a key value for Nato," its secretary general, Jens Stoltenberg, responded. "Two world wars have shown that peace in Europe is also important for the security of the United States. "
Mr Trump has previously called Nato "obsolete" because he longer considered Moscow a threat and described himself as an admirer of Russian leader Vladimir Putin.
The comments are “just hugely dangerous and irresponsible, and completely in character and consistent with his track record but more explicit than ever before”, said Thomas Wright, an expert in national security and US alliances at the Brookings Institution, a Washington think tank.
"It reverses almost 70 years of US policy," Mr Wright said. "If elected, it would potentially spark a very early major crisis because there would be real doubts about whether the US would stand by its commitments in Europe and Asia.
“It is probably the worst thing he has said so far because it was so explicit.”