"The rebalancing of the market is underway, but at a slower pace", the report said, acknowledging it will take more time to tighten the supply-demand balance.
New non-Opec output next year will be more than enough to meet demand growth, the International Energy Agency said Wednesday in its first forecast for 2018.
Oil prices on Friday bounced up off the year's lows as some producers reduced exports and USA rig additions slowed, but the rebound was modest and crude posted its fourth weekly decline on persistent concerns about global oversupply.
Oil slumped to the lowest close in seven months this week as concerns grew that rising US supplies will offset the production curbs by OPEC and allies including Russian Federation.
Inventories fell due to a rise in U.S. crude oil refinery demand to 17,256,000 bpd (barrels per day) on June 2-9, 2017.
Oil set for longest run of weekly losses since 2015 amid glut
The U.S. rig count rose by 8 to 741, extending a year-long drilling recovery to the highest level since April 2015. Even so, output from US shale and other non-OPEC sources will essentially capture the entire gain.
Petroleum prices extended losses on Wednesday after USA government data showed a smaller-than-expected drop in stockpiles of US crude as refineries hiked output.
Both Brent and US crude have given up all the gains since the initial OPEC agreement in late November. The Energy Information Administration (EIA) forecasts that American output will surpass 10 million bpd next year.
"I think there's evidence that we're starting to see reactions by shale producers", said U.S. Bank Wealth Management's Haworth, "New investments are slowing down". Even a fresh agreement in May, between the OPEC and participating non-OPEC producers, failed to lift price.
The global oil market will now focus on the weekly change in the oil rig count data to be released Friday. Also countries like Libya and Nigeria produces more oil.
Oil prices are likely to remain weak until there are signs that USA drilling and future production are shifting onto a more sustainable trajectory.
The measures helped stabilise oil prices at the beginning of the year, with the global benchmark Brent crude sticking above $50 per barrel.