US oil prices dived again today, threatening to dip below $40 a barrel for the first time since the financial crisis and notching their longest weekly losing streak since 1986, as a drop in Chinese manufacturing rattled global markets.

World stock and currency markets joined an extended rout across raw materials this week, a slump accelerated by data showing activity in China's factory sector shrank at its fastest pace in almost 6-1/2 years in August.

With deepening gloom over demand growth from the world's second-biggest oil user, and expectations for a significant build-up in surplus oil stocks this autumn, dealers said most oil traders were unwilling to fight the tide.

"The market is stuck in a relentless downtrend," said Robin Bieber, a director at London brokerage PVM Oil Associates. "The trend is down - stick with it." 

Brent oil fell $1.28, or 2.75 percent, to $45.33 a barrel, threatening to break below $45 a barrel for the first time since March 2009. 

In late 1985, oil prices slumped to $10 a barrel from around $30 over five months as OPEC raised output to regain market share following an increase in non-OPEC production.

Although the current collapse in oil prices, the second this year, has raised alarm within the Organization of the Petroleum Exporting Countries (OPEC), including some of its core Gulf members, there is no indication they will reverse their policy of keeping production wide open to defend market share, delegates told Reuters this week. 

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