Oil prices are set for a fifth consecutive quarter of gains, driven by an impending drop in Iranian exports in the last three months of the year.

london — Oil prices eased on Wednesday but were still set for a fifth consecutive quarter of gains, driven by an impending drop in Iranian exports in the last three months of the year when global demand heats up.

Brent crude futures were last down 21 cents on the day at $81.66 a barrel by 0923GMT, having risen to $82.55 on Tuesday, its highest since November 2014.

US crude futures were down 19 cents at $72.09 a barrel.

The United States will apply sanctions to halt oil exports from Iran, the third-largest producer in the Organisation of the Petroleum Exporting Countries (Opec), from November 4. The pending loss of Iranian supply has been a major factor in the recent surge in crude prices.

Several big buyers of Iranian crude, such as a number of Indian refiners, have signalled they will wind down their purchases, yet the exact impact of the loss of Iranian barrels on the global market balance is not clear. “Iran has the opportunity to channel oil through Iraq and they will still have some buyers in Asia. I’m not totally confident that exports are going to decline by one million barrels per day.

“It is quite a big unknown how big the impact will be but we’ve been cautious in calling for a very, very deep cut in exports. We think it might be more like 500,000 bpd, rather than one million bpd, like in the last round of sanctions,” he said.

Even so, US officials, including President Donald Trump, are trying to assure consumers and investors that enough supply will remain in the oil market and have pushed the likes of Opec to raise output.

“We will ensure prior to the reimposition of our sanctions that we have a well supplied oil market,” Washington’s special envoy for Iran, Brian Hook, told a news conference at the United Nations General Assembly on Tuesday evening.

In an earlier speech at the United Nations, Trump reiterated calls on Opec to pump more oil and stop raising prices. He also accused Iran of sowing chaos and promised further sanctions on the country.