Factors “beyond the control” of oil producers have led prices to surge, the director general of Opec has said.
The cartel's director general Mohammad Barkindo said there were non-fundamental factors influencing the market.
Oil prices have surged in recent weeks in anticipation of US sanctions on Iran, which could take two million barrels per day off the market.
Brent crude reached a four-year high of $86.74 per barrel last week but has since dropped back to $81.52 on Thursday.
Barkindo told the Oil & Money conference in London he was “very concerned” about spare output capacity but that the market was currently well supplied.
Donald Trump criticised Opec and urged its members to “get prices down now” last month, which attracted a backlash from a number of nations, including Iran.
The International Energy Agency boss Fatih Birol urged the world's major oil producers to “take the right steps” to cool the market.
Just hours after Birol's comments last week, Saudi Arabia's energy minister, Khalid al-Falih, said the country would invest $20bn in the next few years to maintain and possibly expand its spare oil production capacity.
Falih said the kingdom had not decided whether to increase its capacity – from a maximum of 12m barrels per day to 13m.