Oil prices fell on Monday as as Russia signaled its output will remain high and concern over the global economy put crude on track for its biggest monthly fall since mid-2016.
Losses were limited ahead of U.S. sanctions on Iranian exports that are expected to reduce supplies when they come into effect in just under a week.
U.S. crude futures ended Monday's session down 55 cents to $67.04. The contract has slumped about 8.5 percent in October, on pace for its largest monthly percentage decline since July 2016.
Brent crude oil futures were down 8 cents at $77.54 a barrel at 1:38 p.m. ET, dropping about 6.3 percent this month and also threatening to post the worst decline since July 2016.
Even with U.S. sanctions on Iranian exports due to come into force on Nov. 4, oil prices have fallen about $10 a barrel since four-year highs reached in early October.
Russian Energy Minister Alexander Novak said on Saturday there was no reason for Russia to freeze or cut its oil production levels, noting that there were risks that global oil markets could be facing a deficit.
The OPEC, led by Saudi Arabia and non-OPEC member Russia, agreed in June to lift oil supplies, but OPEC then signaled last week that it may have to reimpose output cuts as global inventories rise.
"When the Russians start talking about keeping the production levels high and even the possibility that they need to increase it because of a possible tightness in supply, that brought on some selling pressure," said Gene McGillian, director of market research at Tradition Energy in Stamford, Connecticut.
Industrial commodities such as crude and copper have been rattled by hefty losses in global equities due to concern over corporate earnings, and fears over the impact to economic growth from escalating trade tensions.