Donald Trump has said he would likely halt purchases of oil from Saudi Arabia and other Arab allies, unless they seriously commit themselves to the fight against the Islamic State of Iraq and the Levant.

The policy proposal from the Republican frontrunner came as he warned in the wake of the Brussels attacks that jihadists were making the Western world – including Britain – no longer a “safe” place.

In the first in-depth interview on the real estate mogul's foreign policy beliefs, Mr Trump painted a picture of an America crumbling at the seams that can no longer afford to be the policeman of the world.

Mr Trump accused everyone from Arab countries to NATO of "ripping off" the United States, by relying on the country for their security.

“We protect countries, and take tremendous monetary hits on protecting countries," he told the New York Times. "We lose, everywhere. We lose monetarily, everywhere."

Singling out Saudi Arabia, he said that if the country weren’t “without the cloak of American protection,” Mr Trump said. “I don’t think it would be around.”

To rebalance the deal, Mr Trump said, Saudi Arabia should deploy ground troops to fight Isil in Syria and Iraq, or "substantially reimburse" the United States for combating the militant group.