"We're not being reimbursed for the kind of tremendous service that we're performing by protecting various countries," the Republican front-runner was quoted as saying.

Trump said he would boycott oil from Saudi Arabia and other allies ­unless they provide troops or funds to fight ISIS.

"If Saudi Arabia was without the cloak of American protection . . . I don't think it would be around," he told The New York Times.

Trump is open to removing US forces from Japan and South Korea if they did not take on the cost of housing and feeding troops on American bases there, the report said.