World oil prices eased in Asian trading Wednesday ahead of a weekly US report on energy stockpiles expected to reinforce worries over slackening demand, analysts said.

New York's main contract, light sweet crude for September delivery, was 42 cents lower at $121.77 a barrel after slumping $2.54 to $122.19 Tuesday on the New York Mercantile Exchange.

Brent North Sea crude for September delivery eased 29 cents to $122.42 after a drop of $3.13 to settle at $122.71 on Tuesday in London.

Prices have dropped about 17 percent since they touched record highs above $147 a barrel on July 11. The fall is "gigantic in dollar terms," said Victor Shum, of Purvin and Gertz international energy consultancy in Singapore.

He said a stronger dollar and worries about slackening oil demand in the United States, the world's biggest energy consumer, were behind the sharp decline in prices. A stronger dollar makes crude oil more expensive for buyers with weaker currencies. 

Shum said the oil market's bearish mood has also prompted some investors to move their funds out of oil.

The US Department of Energy was to release its weekly report on energy stockpiles in the country Wednesday.

"I think the inventory data will continue to show a demand slowdown in the US and will likely add to the worries over a slackening oil demand," Shum said.

"Markets are finally working as they are supposed to,as higher prices inevitably act as a brake on demand," said John Kilduff, an analyst at MF Global.