Oil prices fell after Trump's tweet, with the price of West Texas Intermediate crude oil - the USA benchmark - falling to a low of $70.86 a barrel, a drop of about 0.58%.
"The OPEC monopoly must get prices down now", Trump insisted in the message. Gas prices are reducing Americans' spendable cash as voters head to the polls for the midterm elections in November.
Oil prices eased on Thursday, slowing an upward surge that had pushed the market toward four-year highs, after U.S. President Donald Trump called on OPEC to "get prices down now!"
The Republican president has lashed out at the Organization of Petroleum Exporting Countries over the past several months, demanding price cuts and output increases in targeted tweets.
US crude oil stockpiles fell for a fifth straight week to 3-1/2 year lows in the week to September 14, while gasoline inventories also showed a larger-than-expected draw on unseasonably strong demand, the Energy Information Administration said on Wednesday.
Decisions are only binding when they are made by all OPEC member states, Zanganeh said, adding that he "will block any decision posing threats to Iran".
Crude inventories fell 2.1 million barrels to 394.1 million barrels, the lowest since February 2015, EIA data showed.
He has consistently complained that oil prices are too high. USA light crude oil was 40 cents higher at $71.52 after rising almost 2 percent on Wednesday.
Trump has consistently complained that oil prices are too high, following a significant uptick in prices that has been passed on at the pump to United States drivers.
US light crude was up 46 cents at $70.77, after earlier touching a high of $71.80.
Investors grappled with the Organization of the Petroleum Exporting Countries and non-OPEC producers' ability to offset a shortfall from Iran due to USA sanctions that go into full force November 4. It's finished. Russian Federation initially cut 300,000 barrels a day of production but then added it all back. However, it said it expects US crude production to outpace that of Russian Federation and Saudi Arabia through next year.
Matters have not been helped by Saudi Arabia's reported comment at the beginning of this month that the kingdom is okay with oil prices remaining steady between $70 per barrel and $80 per barrel.
In a visit to Moscow this month, U.S. Energy Secretary Rick Perry asserted Saudi Arabia, the United States and Russian Federation can between them raise global output in the next 18 months to compensate for falling oil supplies from Iran. Exports of refined products rose by 363,000 barrels a day last week to 5.22 million barrels a day.