Earlier in the session, Brent reached a session low of $75.09 a barrel, the lowest since August 24.
Both contracts have recovered some ground over the last week but are around $10 a barrel below four-year highs reached in the first week of October.
Oil has been caught up in broad financial market slumps this month, with stocks under pressure from the trade war between the world's two largest economies.
Crude output from the world's top three producers, Russia, the United States and Saudi Arabia now jointly account for a third of global oil supplies.
The United States has imposed tariffs on $250 billion worth of Chinese goods, and China has responded with retaliatory duties on $110 billion worth of USA goods.
Prices received some support on Tuesday after reports that Trump thinks "a great deal" with China is possible on trade. He did not elaborate.
It should be noted that the oil trade is controlled by the state.
Speaking to Shana, Saeed Khoshroo, the director of worldwide affairs at NIOC, said the prices were charged based on the global oil prices; therefore, if the traded shipments were quoted lower during IRENEX Sunday session than the base price announced by NIOC in an earlier announcement, it was because of price fluctuations in the global market.
Oil faced "downward pressure from lower growth forecasts around the globe", said Alfonso Esparza, senior market analyst at futures brokerage Oanda.
"Many countries have shown readiness to do business with Iran" despite USA sanction threats, Zarif was quoted as saying, Xinhua news agency reported. "The second one is global economic growth momentum slowing down", said IEA chief Fatih Birol.
Iran's seaborne crude exports have fallen from a 2018 peak of just over 2.5 million bpd in May to around 1.5 million bpd in September and October, Eikon data showed.
Data from the U.S. Energy Information Administration last Wednesday revealed that U.S. crude stockpiles rose for a fifth straight week.
Even with US sanctions on Iranian exports due to come into force on November 4, oil prices have fallen about $10 a barrel since four-year highs reached in early October.
On May 8, President Donald Trump announced he was pulling the U.S. out of the 2015 Iran nuclear deal and promised to hit Tehran with sanctions on the country's energy oil and financial sectors despite objections from other parties to the agreement.
"With the imminent return of a new wave of sanctions, the government is determined to utilise the manoeuvering ability of the private sector to sell Iran's oil and find new markets", Hamidreza Salehi, director of Iran's energy exports federation, told semi-official news agency ILNA.