Donald Trump said on Saturday he had received assurances from King Salman of Saudi Arabia that the kingdom would increase oil production "maybe up to 2,000,000 barrels", in response to turmoil in Iran and Venezuela.

President Trump said Saturday that he persuaded the king of Saudi Arabia to increase oil production in an effort to lower gas prices in the U.S.

"Prices to high! He has agreed!" the tweet said, .

Iran is the fifth-largest oil producer in the world, pumping about 4.7 million barrels per day (bpd), or nearly 5 per cent of total output, much of it to China and other energy-hungry nations such as India.

Investors are betting Saudi Arabia has little room to respond to a future crisis should it boost output even more to meet Trump's request, as Saudi Arabia only has about 2 million barrels of unused capacity, according to International Energy Agency.

The statement, however, did not mention any intention by Saudi Arabia, the world's top oil exporter, to raise production to 2 million barrels per day. But broadcasting its requests on Twitter with a number that stretches credibility opens a new chapter in U.S. -Saudi relations, Halff said.

It added that there also was an understanding that oil-producing countries would need "to compensate for any potential shortage of supplies".

"This is a situation where U.S. shale oil production itself has dropped in the past few months and that drop in the inventory has pushed oil prices up", Jordan said.

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That agreement sought to curb Tehran's nuclear capabilities in exchange for the lifting of some sanctions.

Iranian leaders held a meeting on Saturday to examine countermeasures to United States economic sanctions, including ways to keep exporting oil, according to a report in the Iranian news agency IRNA.

"All the potential shortfalls could outstrip the production increase agreed to by OPEC and Russian Federation", said Dominick Chirichella, Director of Risk Management at EMI DTN.

Al Jazeera's Rosiland Jordan, reporting from Washington, DC, said "it is not unusual" for the White House to put pressure on OPEC members to increase oil output "mainly because the U.S. president is first and foremost concerned about the cost of gasoline and consumer fuels, especially in an election year" - the USA will hold midterm congressional polls in November.

"Saudis are used to USA requests for oil", Halff said.

The administration has threatened close allies such as South Korea with sanctions if they don't cut off Iranian imports by early November.

China is the largest importer of Iranian oil with 24 per cent, followed by India with 18 per cent. Turkey stood at 9 per cent and Italy at 7 per cent. There's a risk that supplies from Iran could be cut further as there's pressure on other countries to join the United States in sanctions, he said.