NEW YORK - OIL prices tumbled to five-week lows on Monday on growing evidence of an extended recession that could mean demand for energy will remain weak for some time.

Benchmark crude for August delivery fell US$2.67 - or 4 per cent - to US$64.05 (S$96) a barrel in afternoon trading on the New York Mercantile Exchange.

It was the fourth straight day of declines on Nymex and since the beginning of the month, crude prices have fallen about 8 per cent. Natural gas prices plunged as well.

Major energy users, like industrial manufacturers, have been hit hard by the recession and unemployment data released last week in both the US and Europe doused hopes for a quick recovery.

'The recent evidence concerning the US economy is terrible. The news regarding Europe seems no better,' said economist Philip Verleger. 'This suggests oil use will continue to decline for another year.'

Oil prices had been rising for months on the belief that the economy would improve by the end of the year. Prices have also been pushed higher by the weak US currency.

Because crude is bought and sold in dollars, it essentially becomes cheaper when the dollar falls against other currencies. And the dollar has fallen steadily with the US government spending billions to prop up major banks and the auto industry.

Doubts about how long the weak US currency can sustain prices have begun to tamp down prices.

Even last week, when oil prices hit an eight-month high above US$73 per barrel, it was another sign of how volatile the market has become. A barrel of oil fell midway through the day last Tuesday and prices have been declining since.

The spiking price of energy had baffled experts because demand for everything from crude to gasoline is dismal. The US is mired in recession and Americans are driving billions fewer kilometres than they have in past years. -- AP