Under existing curbs, OPEC, led by Saudi Arabia, and non-OPEC producers, led by Russia, have cut just over 7 million barrels per day (bpd), while Saudi Arabia has made an additional voluntary reduction of 1 million bpd.
Brent crude was down $1.02, or 1.6%, at $63.96 a barrel by 1334 GMT. West Texas Intermediate US oil was off by $1.16, or 1.9%, at $60.40 barrel.
"The wobble we have seen in prices means that OPEC+ will likely need to take a cautious approach once again," bank ING said. "We are of the view that the group will likely hold output levels unchanged."
Brent crude fell 50 cents, or 0.74%, to $67.50 a barrel by 1150 GMT after dropping 0.82% on Wednesday.
Short-term developments - stuttering vaccine rollouts and the build in US oil inventories - are driving sentiment, but the longer-term oil outlook is still encouraging.
The market has drifted lower over the past few days as more European countries pause inoculations of AstraZeneca's COVID-19 vaccines due to concerns over possible serious side effects, which could slow a recovery in fuel demand.