Oil prices fell in early Asian trading on Tuesday on expectations that producer cartel OPEC and key ally Russia will gradually increase output after withholding supplies since 2017.
Brent crude futures, the international benchmark for oil prices, were at $78.05 per barrel at 0021 GMT, down 29 cents, or 0.4 percent, from their last close.
U.S. West Texas Intermediate (WTI) crude futures were at $65.63 a barrel, down 22 cents, or 0.3 percent.
The Organization of the Petroleum Exporting Countries (OPEC) together with a group of non-OPEC producers that includes Russia started withholding oil supplies in 2017 to end a global glut and prop up prices.
Following a sharp increase in crude prices from their sub-$30 per barrel lows in 2016, the group on June 22 will meet in Vienna, Austria, to discuss forward policy.
Greg McKenna, chief market strategist at futures brokerage AxiTrader said there would likely be oil price volatility in the week ahead of the meeting.
"OPEC is fractured or fracturing," McKenna said, as Iran, Venezuela, and Iraq "seek to veto the production increase".
"We could be seeing the long-term relationship between the Saudis and Russia pushing OPEC into second place," he added.