In early Asia, Brent crude was up 12 cents, or 0.3%, at $40.58 a barrel by 0039 GMT, having dropped more than 3% overnight. U.S. oil was up 13 cents, or 03%, at $38.69 a barrel, after also declining more than 3% on Monday.
OPEC's Mohammad Barkindo, asked at the virtual India Energy Forum by CERAWeek if the second wave of the virus required any changes to OPEC+ strategy, said hopes earlier this year of a demand rebound had been disappointed.
Brent crude was down 70 cents, or 1.7%, at $41.07 by 0353 GMT. U.S. West Texas Intermediate (WTI) dropped 69 cents, or 1.7%, to $39.16, having fallen more than a dollar shortly after the start of trading.
Brent crude was down by 53 cents, or 1.3%, at $41.24 by 0052 GMT. U.S. West Texas Intermediate (WTI) dropped 53 cents, or 1.3%, to $39.32, having fallen more than a dollar shortly after the start of trading.
Brent crude futures for December delivery were at $42.94 a barrel, down 22 cents, or 0.5%, as of 0035 GMT, while December U.S. West Texas Intermediate (WTI) crude futures slipped 23 cents, or 0.7%, to $41.47 a barrel.
Brent crude futures fell 30 cents, or 0.7%, to $42.32 a barrel by 0149 GMT, after falling 31 cents on Monday.
The Organization of the Petroleum Exporting Countries (OPEC) and allies including Russia, collectively known as OPEC+, have been reducing output since January 2017 in an effort to balance the market, support prices and reduce inventories.
The document presented scenarios that included a base case that still showed a deficit in 2021 of 1.9 million barrels per day (bpd) on average, albeit less than the deficit of 2.7 million bpd forecast in the previous month's base case.
A further weakening of demand could threaten plans by OPEC and allies to taper in 2021 the record oil output cuts they made this year.
The return of supply comes as resurgent COVID-19 infections in the U.S. Midwest and Europe raise worries about fuel demand growth, posing a challenge for the Organization of Petroleum Exporting Countries and its allies, together called OPEC+.
Brent crude for December fell 55 cents, or 1.3%, to $42.30 a barrel by 0023 GMT and U.S. West Texas Intermediate for November was at $40.08 a barrel, down 52 cents, or 1.3%.
U.S. West Texas Intermediate (WTI) crude oil futures fell 87 cents, or 2.1%, to $39.80 a barrel by 0104 GMT while Brent crude futures fell by 74 cents, or 1.7%, to $41.91 a barrel.
Brent crude slipped on the news and was down 78 cents, or 1.9%, at $40.53 a barrel at 0516 GMT. U.S. oil was 79 cents, or 2%, lower at $37.93.
Brent crude was down 36 cents, or 0.9%, at $40.57 a barrel at 0055 GMT, after falling more than 3% on Thursday. U.S. oil was also 36 cents, or 0.9%, lower at $38.36, having fallen nearly 4% in the previous session.
But demand worries remain. Concerns are growing in New York, where COVID-19 infection rates continued to climb
Brent crude dropped 23 cents, or 0.6%, to $41.03 per barrel by 0048 GMT. West Texas Intermediate fell 26 cents, or 0.7%, to $39.29.
U.S. West Texas Intermediate (WTI) crude futures slipped 17 cents, or 0.4%, to $40.43 at 0120 GMT, while Brent crude futures also fell 17 cents, or 0.4%, to $42.26 a barrel. Both benchmarks rose about 1% on Monday.
Brent crude fell 23 cents, or 0.6%, to $41.69 a barrel by 0243 GMT after dropping 2.9% last week. U.S. West Texas Intermediate was at $40.04 a barrel, down 21 cents or 0.5%, following a 2.1% decline last week.
Brent crude was down 2 cents at $41.92 a barrel by 0113 GMT, while U.S. West Texas Intermediate (WTI) crude was 3 cents firmer at $40.34.
Those fears prompted a rally in the dollar as investors turned to safer assets, adding pressure to oil prices. A stronger dollar makes oil, priced in U.S. dollars, less attractive to global buyers.
Authorities in the United States and Brazil are investigating improper payments to officials at Petrobras, Brazil's state-run oil company, as part of Brazil's far-reaching corruption probe, known as Car Wash. The latest U.S. court filings shed new light on the role of energy traders in a scheme that has led to charges against hundreds of powerful business leaders and politicians.
U.S. West Texas Intermediate (WTI) crude futures for October, due to expire on Tuesday, rose 26 cents, or 0.7%, to $39.57 a barrel at 0224 GMT. The more active November contract rose 15 cents, or 0.4%, to $39.69.
Brent crude was down 20 cents, or 0.5%, at $42.95 a barrel by 0039 GMT, while U.S. crude fell by 27 cents, or 0.7%, to $40.84 a barrel.
Brent crude was down 6 cents at $43.24 a barrel by 0112 GMT, while U.S. oil futures dropped 6 cents to $40.91 a barrel. Both contracts have risen sharply this week as Hurricane Sally cut U.S. production and are on track for a weekly gain of around 9%, the first in three weeks.
U.S. West Texas Intermediate (WTI) crude futures were flat at $40.16 a barrel at 0118 GMT, after jumping 4.9% on Wednesday.