Oil prices fell for a second day on more troubling signs for the world economy.
Benchmark US crude dropped by $1.36 to $101.10 per barrel in afternoon trading on the New York Mercantile Exchange.
Brent crude lost $2.26 to $120.41 per barrel in London.
Global stock markets also fell, along with the prices of most other commodities.
A number of reports raised concerns about economic growth. A private survey showed that US small business owners were increasingly worried about high fuel prices.
The government said wholesalers restocked their shelves at a slower pace at the beginning of the year. And China said that European demand for its manufactured goods is declining - one more sign that the world's second-biggest economy is slowing.
Those reports follow last week's disappointing US jobs report. The government said that employers added only 120,000 jobs in March - half as much as the previous three months.
The impact of high oil prices on the economy is now more of a concern to the market than a possible military conflict in Iran, analysts say.
Oil prices could fall further in coming months if Iran agrees to negotiate with the United Nations over its nuclear program. The oil-rich nation is expected to resume talks with members of the UN Security Council this weekend.
Western nations fear Iran is building a nuclear weapon. They've imposed sanctions meant to shrink Iran's oil revenue and force it to open its facilities to inspection. Iran denies the claims, and has rejected inspections.
Earlier today, Iran said it cut off oil shipments to Greece. President Mahmoud Ahmadinejad asserted that his country can get by for two or three years without selling more oil.
In other energy trading, heating oil gave up 5.09 cents to $3.095 per gallon and fuel futures lost 4.89 cents to $3.2478 per gallon. Natural gas fell by 5 cents to $2.057 per 1,000 cubic feet.
