Oil prices edged lower on Sept. 20 ahead of an expected build in U.S. crude oil stocks and on Venezuelan comments that the oil market remains oversupplied by 10%.

Analysts polled by Reuters expect U.S. commercial crude oil inventories to have risen 2.3 million barrels (MMbbl) in the week to Sept. 16, paving the way for a bearish market reaction because a rise in stocks indicates growing oversupply.

The American Petroleum Institute (API) is scheduled to release its weekly crude stocks data at 3:30 p.m. CT (20:30 GMT) on Sept. 20.

Brent crude oil futures were trading at $45.45/bbl at 6:28 a.m. CT (11:28 GMT), down 50 cents day on day and a near three-week low. U.S. West Texas Intermediate (WTI) crude futures were down 44 cents at $42.86/bbl.

Oil prices also reacted to comments made by Venezuela's Oil Minister Eulogio Del Pino on Sept. 19 that global oil supply of 94 MMbbl/d needs to fall by about a tenth if it is to match consumption.

Members of OPEC and other oil producers are set to hold an informal gathering in Algiers next week, which the oil market hopes could lead to an agreement to freeze production levels.

Algeria's Energy Minister Noureddine Bouterfa said on Sept. 20 he was "optimistic" participants would reach consensus on how to prop up the oil market.

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"I would not be surprised to see some short-covering in the second half of this week just ahead of the informal OPEC meeting," said Tamas Varga, lead oil analyst at London brokerage PVM Oil Associates.

Official data released late on Sept. 19 confirmed a rise in Saudi Arabian oil exports in July to 7.622 MMbbl/d, up from 7.456 MMbbl/d in June.

"[An output freeze] would only secure an even higher push of Saudi crude oil and would be a case where the proposed cure is worse than the disease," said Olivier Jakob, managing director of PetroMatrix in Switzerland.

A fire at Saudi Arabia's Ras Tanura oil terminal which broke out the morning of Sept. 20 and injured eight people did not affect operations and was extinguished, operator Saudi Aramco said.

Technical market indicators were also weak, with WTI likely to test support at $42.78/bbl soon, after which a fall towards $42 would be likely, according to Reuters analyst Wang Tao.

For Brent, he said prices may test support at $45.63/bbl and, failing to hold that level, could fall to just more than $45/bbl.