Oil prices extended their decline in Asia Friday after the OPEC cartel indicated that current lofty output levels will remain, while a stronger dollar is also causing downward pressure.
US benchmark West Texas Intermediate for September delivery fell 32 cents to $48.20 and Brent crude for September shed 24 cents to $53.07 a barrel in afternoon trade.
Both contracts tumbled on Thursday, snapping two consecutive days of gains.
Abdullah El-Badri, Secretary General of the Organization of the Petroleum Exporting Countries, said the group would not cut output in response to lower prices.
Speaking in Moscow after meeting Russia's energy minister on Thursday, he said the cartel is "not ready" to cut production, which is currently at around 30 million barrels per day.
Analysts said the statement shows OPEC is determined to defend its market share as it fends off competition from US shale oil.
"OPEC is telling the market that cuts will not come from them," said Daniel Ang, an investment analyst with Phillip Futures in Singapore.
OPEC is "emphasising that it is fighting for market share", he added.
At its most recent meeting in Vienna in June OPEC kept its output levels despite a supply glut, which has depressed oil prices.
Prices are also under pressure by the strength of the US currency, which makes dollar-priced oil more expensive to holders of weaker units, dampening demand.
The dollar has picked up steam on expectations the Federal Reserve will raise US interest rates later this year.
The chances of a September lift were raised Thursday after data showed the US economy expanded 2.3 percent in April-June, the strongest pace since the third quarter of 2014.
"The second-quarter GDP data support the Fed's more upbeat tone on economic conditions and suggests that the economy could cope with higher interest rates," research firm Capital Economics said.