International Brent crude oil futures LCOc1 were trading at $49.32 per barrel at 0558 GMT, down 60 cents, or 1.2%, from their previous close, Reuters wrote.
U.S. West Texas Intermediate (WTI) crude futures were down 66 cents, or 1.39%, at $46.98 a barrel.
Prices have fallen by over 3.5% since their August peaks.
Traders said the price falls were a result of climbing output from the Middle East, where oil exports from Iraq's southern ports have averaged 3.205 million barrels per day (bpd) in August, exceeding the average level seen in July, according to two officials from state-run South Oil Company. Exports in July averaged 3.202 million bpd.
Iran said late last week that it would only cooperate in upcoming producer talks in September if other exporters recognized Tehran's right to regain market share lost during international sanctions that were only lifted in January.
Analysts said disagreements within the Organization of the Petroleum Exporting Countries, and especially its key members Saudi Arabia and Iran, meant few expected a significant impact on global output from the talks, according to Reuters.
"The market is increasingly likely to discount the outcome of the event, given, even in the instance of a freeze being agreed, compliance will be an issue," Barclays said.
Despite this, Barclays said that it saw "incoming oil market data (both demand and supply) as a source for price strength in Q4," according to Reuters.