Goldman Sachs on Monday forecast a tighter oil market for longer amid strong demand growth and the likelihood that rising supply disruptions could counter any increase in OPEC production.

"Our updated global supply-demand balance continues to point to further declines in inventories and higher oil prices in 2H18," the bank said, reiterating its Brent price forecast for a peak of $82.50 per barrel during the summer and a year-end estimate of $75.

"We continue, however, to view the risks to this forecast as skewed to the upside, even if concerns over demand and higher OPEC production weigh on prices near term."

Oil prices on Monday extended last week's losses, partly on expectations that top suppliers Saudi Arabia and Russia could increase production after withholding output since the start of 2017.

The producer cartel of the Organization of the Petroleum Exporting Countries (OPEC) and allies including Russia will meet in Vienna on June 22 to decide forward production policy.

The current market pricing suggests that meeting could have a bullish impact on oil prices, especially following the recent decline in net speculative length, Goldman said.

"The Brent option market may be underpricing the event risk... We see the Brent moves since May 24 as pricing-in a higher level of OPEC and Russia production increase than we and consensus are expecting."

The bank said it expects core OPEC and Russia production to increase by 1 million barrels per day by year-end and by another half a million barrels per day in the first half of 2019, but would be offset by increased disruptions in Venezuela and Iran.

"Our updated fundamental oil balance shows...that the oil market remains in deficit with resilient demand growth and rising disruptions requiring higher core OPEC and Russia production to avoid a stock-out by year-end."

After this week's meeting, Goldman said it believes the tightness of the oil market will be the catalyst for Brent prices to rally, through steeper backwardation.

(Reporting by Apeksha Nair in Bengaluru Editing by Manolo Serapio Jr.) ((Apeksha.Nair@thomsonreuters.com; within U.S. +1 651 848 5832, outside U.S. +91 80 6749 6408/1298; Reuters Messaging: apeksha.nair.thomsonreuters.com@reuters.net))