Reuters reports: Oil consuming nations, hedge funds and big oil refineries are quietly preparing for a Doomsday scenario: An attack on Iran that would halt oil supplies from OPEC’s second-largest producer.

Most political analysts and oil traders say the probability of military action is low, but they caution the risks of such an event have risen as the West and Israel grow increasingly alarmed by signs that Tehran is building nuclear weapons.

That has Chinese refiners drawing up new contingency plans, hedge funds taking out options on $170 crude, and energy experts scrambling to determine how a disruption in Iran’s oil supply — however remote the possibility — would impact world markets.

With production of about 3.5 million barrels per day, Iran supplies 2.5 percent of the world’s oil.

“I think the market has paid too little attention to the possibility of an attack on Iran. It’s still an unlikely event, but more likely than oil traders have been expecting,” says Bob McNally, once a White House energy advisor and now head of consultancy Rapidan Group.

Rising tensions were clear this week as Iranian protesters stormed two British diplomatic missions in Tehran in response to sanctions, smashing windows and burning the British flag.