Oil edged higher on Thursday, driven by the prospect of a shortfall in global supply once U.S. sanctions against major crude exporter Iran come into force in just five weeks' time. U.S. President Donald Trump last week demanded that OPEC raise production to prevent further price rises ahead of key congressional elections in early November. Analysts say the Organization of the Petroleum Exporting Countries and partner Russia appear unlikely at this point to respond immediately to Trump's demands, while U.S energy secretary Rick Perry has also ruled out using U.S. strategic crude reserves as a means of lowering the price.

The most-active December Brent crude futures contract was up 21 cents at $81.55 a barrel at 2:19 p.m. ET, after earlier approaching Tuesday's four-year high of $82.55. The front-month November contract expires on Friday. U.S futures ended Thursday's session 55 cents higher at $72.12 a barrel. "On paper, you could argue that the technical and fundamental perspective points to higher prices, so I think that will carry on into next week and further out," Saxo Bank senior manager Ole Hansen said. "$100 dollars barrel, I am struggling to see that. Already at $80, we are seeing emerging-market local oil prices pretty close to where we peaked a few years ago ... the race to protect consumers from further price rises from here could potentially impact demand growth sooner than would otherwise have been expected." Estimates of how much Iranian crude could disappear from the market once U.S. sanctions come into force on Nov. 4 vary widely among the analyst community, from anywhere from 500,000 barrels per day (bpd) all the way to 2 million bpd. At its 2018 peak in May, Iran exported 2.71 million bpd of crude oil, equivalent to nearly 3 percent of daily global consumption.