Washington: Republican presidential frontrunner Donald Trump has demanded that the US allies need to up the ante up if they want to continue under the "cloak of American protection."

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

Trump said he would stop buying oil from Saudi Arabia and other allies if they fail to 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.

The Republican candidate said that it is getting expensive to keep "defending the world." "We defend everybody. When in doubt, come to the United States. We'll defend you. In some cases free of charge," he said.

Trump also pushed back against suggestions that he was following an "isolationist" foreign policy. "I am "America First," " he said. "I like the expression."

Trump said that there is a need to renegotiate the Iran deal to extend restrictions on the country's ability to build nuclear weapons. "We gave them $150 billion, and they can't spend it in our country," he said.

"We have been disrespected, mocked and ripped off for many, many years by people that were smarter, shrewder, tougher," he added.