US West Texas Intermediate crude oil futures traded at about $68 per barrel on Tuesday, while Brent crude futures sat at nearly $78.
"If there was not that set of sanctions, I think prices would go to $70 or even a little bit lower. But now the sanctions threat is real and less than two months in front of us, that will transform the market into much higher prices," Fereidun Fesharaki, founder and chairman of consultancy FACTS Global Energy, told CNBC at the CLSA Investors' Forum in Hong Kong.
"The higher price will only be blamed on the Trump administration. There's not much anybody can do if the sanctions come," he said on Tuesday.
US President Donald Trump's decision to withdraw from an international agreement to curb Iran's nuclear program has resulted in a round of sanctions being reimposed on the country's financial, automotive, aviation and metals sectors. The US State Department has set Nov. 4 as a deadline for Iranian oil buyers to completely cut their purchases to avoid American sanctions.
Iran is currently one of the largest oil exporters in the world. Cutting off Iranian supplies entirely would push oil prices above $100 per barrel because other major producers could not easily fill the void, said Fesharaki.
Trump said on Twitter in July that energy prices were too high and urged the Organization of the Petroleum Exporting Countries to reduce prices. But OPEC and Russia don't have the spare capacity to ramp up supply much more, Fesharaki said.
US shale producers are also running close to their maximum capacity, he said. So, "it's a fallacy to believe that US shale can fill the Iran void. Zero impact," he added.
The timing for oil prices to hit $100 per barrel — a level not seen since 2014 — depends on how quickly the US and China resolve their differences on the trade front, Fesharaki noted.
Ongoing friction between the two largest economies in the world has affected sentiment. If that leads to a slowdown in global economic activity, the oil and gas industry will be dampened, Fesharaki said.
"At the moment, what is holding (oil prices) from going up is the fear, macroeconomic fears," he said. "If the US-China deal is settled, the price of oil only has one way to go: up."