* Few analysts expect producers to agree freeze in output

* U.S. crude inventories swell to 523.6 million barrels

* China July oil demand down 0.3 pct at 10.58 million bpd

(Updates throughout, changes dateline, previous SINGAPORE)

By Christopher Johnson

LONDON, Aug 25 (Reuters) - Oil prices slipped on Thursday as the market focused on oversupply and fading hopes of a production freeze.

Global crude oil benchmark Brent was down 15 cents at $48.90 a barrel by 0830 GMT, having closed down 1.8 percent on Wednesday. U.S. light crude oil was unchanged at $46.77 a barrel, after dropping 2.8 percent on Wednesday.

Oil prices rose more than 20 percent in the first three weeks of August on talk of a potential deal by oil exporters to freeze production levels to try to support prices.

Members of the Organization of the Petroleum Exporting Countries will meet on the sidelines of the International Energy Forum, which groups producers and consumers, in Algeria on Sept. 26-28.

But hopes of a deal have been dampened by record OPEC output and few analysts see the prospect of voluntary restrictions.

"Speculators pushed the price up on expectations of an output freeze, which is unlikely to happen," said Carsten Fritsch, senior oil analyst at Commerzbank in Frankfurt. "I see downside risks if those expectations are being scaled back."

U.S. investment bank Jefferies agreed, telling clients on Thursday that even if a freeze was agreed, "the effects on the physical market would appear to be minimal".

"We do not expect a production freeze - let alone a production cut - from the OPEC meeting," it said in a report.

With output near record levels from many of the top producers, and demand shaky, there seems little prospect of an end to the glut which has pulled down crude prices from over $100 a barrel in 2014 to their current sub-$50 levels.

High storage levels are also weighing on the market.

In the United States, commercial crude oil stocks rose by 2.5 million barrels to 523.6 million barrels, 16 percent higher than a year ago.

In refined products, stocks around the world are also brimming as demand slows while refinery output remains high.

"Ample inventories were due to weaker demand in Asia, but more generally were driven by excess supply generated by refiners maximising runs, notably to produce gasoline in the U.S.," BNP Paribas said.

China's implied oil demand fell 0.3 percent from a year earlier to 10.58 million barrels per day (bpd) in July, according to Reuters calculations using official data. (Additional reporting by Henning Gloystein in Singapore; editing by Jason Neely) ((christopher.johnson@thomsonreuters.com; +44 7790 561 651; Reuters Messaging: christopher.johnson.reuters.com@reuters.net))