On Monday, Brent crude surged above $83 per barrel as Iran continues losing its crude exports ahead of United States sanctions which come into force in November.
Crude has rallied about 16 percent since mid-August as supply losses from Iran to Venezuela continued to rattle global markets.
Brent has risen by more than 20% from its most recent lows in August, Reuters reported.
Estimates vary widely on how much Iranian crude USA sanctions could remove from the market, from 500,000 barrels per day (bpd) to 2 million bpd.
The U.S. remains in a trade fight with China that could have even larger implications for global oil demand if the spat gets worse. "Any geopolitical tension that we don't foresee coming, with such low spare capacity, is the thing that would push oil to $100 a barrel", he said in a Bloomberg TV interview.
But for now the focus is USA sanctions on Iran's energy industry, which come into force on November 4 and are created to cut crude exports from the third-biggest producer in the Organization of the Petroleum Exporting Countries.
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WTI prices were supported by a stagnant rig count, which points to a slowdown in US crude production C-OUT-T-EIA .
US light crude futures were up $1.13 at $74.34 a barrel, also the highest in almost four years. To this, Iran replied crude wouldn't have edged up without the USA interference in the affairs of the Middle East.
The global crude oil benchmark LCOc1 lost 48 cents to $84.50 per barrel by 1002 GMT after reaching a new four-year high of $85.45 in the previous session.
With crude prices soaring and many currencies in emerging markets, including India's rupee and Indonesia's rupiah declining, analysts warn that economic growth may be eroded.
The survey revealed that Libya, Angola, Saudi Arabia, and Nigeria provided the biggest output increases in September, while the biggest drop was provided by Iran at 100,000 bpd.
Trump's been increasing the pressure on OPEC, saying it's pushing oil prices too high. Britain's Barclays bank, however, said on Tuesday that "OPEC has ample spare capacity".