US Election 2016: Trump laments 'ripped off' America
The frontrunner for the Republican nomination for the November election was speaking to the New York Times.
Mr Trump said he would consider pulling out troops from Japan and South Korea if they did not pay the US more.
He said he might stop buying oil from Saudi Arabia if it did not send troops to fight so-called Islamic State.
Mr Trump insisted he was "not isolationist" but "America First".
He said: "We have been disrespected, mocked, and ripped off for many, many years by people that were smarter, shrewder, tougher.
"We were the big bully, but we were not smartly led. And we were the big bully who was the big, stupid bully and we were systematically ripped off by everybody."
The thrust of Mr Trump's interview concerned the economic cost of US foreign policy.
Mr Trump cited the US debt - "soon to be $21tn" (£14.8tn) - and linked it to the fact the US "defended the world".
"No matter who it is, we defend everybody. When in doubt, come to the United States. We'll defend you. In some cases free of charge."