NEW YORK, Nov. 22 (Xinhua) -- Oil prices retreated on Monday as investors worried that the Irish debt problems would spread and hurt European economic stability.

Ireland on Sunday formally requested help from other countries in the European Union as its debt problems deepened. Terms of the package from the European Union and the International Monetary Fund were still under negotiation but should not exceed 137 billion U.S. dollars.

The worries about the Irish debt problems also weakened the euro and bolstered the dollar. A strong dollar usually makes dollar-priced oil go down.

Meanwhile, China's central bank on Friday announced its decision to raise required reserve ratio of commercial banks for the second time in less than ten days to curb inflation, which made investors worry that the demand for energy would be weakened.

The benchmark crude oil for January delivery fell 24 cents on Monday to settle at 81.74 dollars a barrel on the New York Mercantile Exchange. Brent crude lost 38 cents to settle at 83.96 dollars a barrel on the ICE Futures exchange.