DONALD Trump has threatened to withdraw military aid from a NATO ally under attack if he becomes president.

The billionaire businessman said he would first consider how much they had financially contributed to the alliance before pitching America’s military might in.

4 Donald Trump has pledged to put America's interests first Credit: EPA

4 Trump has chosen Mike Pence as his running mate in the US presidential race Credit: AP:Associated Press

4 Trump is keen to slash military spending and has raised prospect of leaving expensive alliances Credit: AP:Associated Press

The Republican candidate insisted other countries in the 67-year alliance should share more of the costs long borne by Washington. He even raised the prospect of pulling out of treaties where he believes the burden is too great on the US.

Trump said he would “prefer to be able to continue” with existing alliances but only if all members pulled their weight and stopped relying on America’s deep pockets.

Speaking ahead of his address to the Republican convention where he will press his nationalistic “America First” agenda, he told the New York Times: “We are going to take care of this country first,” he said, “before we worry about everyone else in the world.”

The former reality TV star also suggested the US would only protect the Baltic states against Russian aggression based on their contribution to the alliance.

Asked if the US would automatically come to their aid, he said: “If they fulfil their obligations to us, the answer is yes.”

4 A naval officer inspects a Russian destroyer moored in the Crimea which the Russians seized in 2014 Credit: EPA

Trump also told the paper he would not pressure Tukey or other similar authoritarian allies to end crackdowns on political opponents or the suppression of civil liberties.

He said the US should try to “fix our own mess” before interfering in the domestic affairs of other countries.

“I don’t think we have a right to lecture,” he said. “Look at what is happening in our country. How are we going to lecture when people are shooting policemen in cold blood?”

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His comments raise fears about the country’s continued role as a peacekeeper and protector of human rights. Trump appeared to suggest the US would only continue to intervene if there was something in it for the country.

Trump repeated threats to withdraw tens of thousands of US troops from foreign bases like Japan and South Korea because the US would “spending a fortune on military”.

The real estate tycoon has been confirmed as the Party’s presidential candidate

at the Republican’s convention.