DONALD Trump may stop the US from automatically defending allies under attack, saying he would first consider their contribution to allegiance with the US. 
Mr Trump made the remarks in an interview with the New York Times, threatening to pull back US military services deployed internationally.
He was specifically referring to the US relationship with NATO allies, but the -approach could leave Australia exposed in Asia.
Further, the same isolationist logic could flow to the US's relationship with Australia.
And what this would mean for the US troop presence in Darwin is not known. The New York Times said Mr Trump "gave no ground", including on proposed dealings with China in the South China Sea and North Korea on missile threats.
Mr Trump has previously raised questions about defending allies, but the latest interview set out the conditions on which he would judge what was worthy - specifically contributions to the allegiance with the US.
"If we decide we have to defend the US, we can always deploy from American soil," Mr Trump said. "And it will be a lot less expensive." In the interview, Mr Trump repeated his hardline insistence that other countries should start sharing more of the defence costs long borne by Washington.
Mr Trump told the Times that the US was "spending a fortune on military in order to lose $800 billion".
"That doesn't sound very smart to me." He told the Times he would "prefer to be able to continue" existing agreements, but that allies were taking advantage of the US.Mr Trump said he believed US allies would "understand" his new approach.