Oil prices will struggle to break out of current ranges this year as a spike in the Delta coronavirus cases threatens to slow a demand recovery, a Reuters poll showed on Tuesday.

The survey of 43 participants forecast Brent would average $68.02 a barrel in 2021 versus a forecast in July for $68.76. It is the first downward revision to the 2021 price view since November 2020.

Brent has averaged about $67 this year.

"With the Delta variant in play weighing on demand and price sentiment, overheating in oil prices is unlikely in the near term," said DBS Bank analyst Suvro Sarkar.

The International Energy Agency said this month oil demand was set to increase more slowly for the rest of 2021 on the spread of the Delta variant. 

But the Organization of the Petroleum Exporting Countries has so far stuck to its prediction of a strong demand recovery.

OPEC and its allies, or OPEC+, agreed in July to boost output by 400,000 barrels per day a month starting from August until its current reductions of 5.8 million bpd are phased out.

Some analysts said the group, which meets on Wednesday, could reconsider hiking output due to the impact of rising COVID-19 cases. Others downplayed the hit to consumption.

"The decision to boost OPEC+ production was reasonable in the light of strong oil demand and high inflation numbers. But the question might be if OPEC+ will really stick to their plan if demand slows down because of possible COVID Delta problems," LBBW analyst Frank Schallenberger said.

U.S. crude was forecast to average $65.63 in 2021 versus $66.13 in July, amid a slow recovery in production.

Commerzbank analyst Carsten Fritsch predicted a "gradual, unspectacular increase (in U.S. output), not strong enough to cause any headaches for OPEC+."

The U.S. Energy Information Administration had forecast output to fall 160,000 barrels per day (bpd) in 2021 to 11.12 million bpd.

(Reporting by Eileen Soreng and Arundhati Sarkar in Bengaluru; Editing by Edmund Blair) ((eileen.soreng@thomsonreuters.com; Within U.S. +1 646 223 8780, Outside U.S. +91 80 6749 6131; Reuters Messaging: eileen.soreng.thomsonreuters.com@reuters.net))