Singapore - Crude prices were down in Asia on Tuesday as the euro retreated against the dollar after Standard & Poor's placed major European countries on negative credit rating watch, analysts said.
New York's main contract, light sweet crude for January delivery, fell 50 cents to $100.49 a barrel.
Brent North Sea crude for delivery in January shed 58c to $109.23.
Crude prices tracked the euro's fall after S&P warned Germany, France and four other AAA eurozone nations that they risked losing their top ratings within 90 days, analysts said.
"Crude oil prices gave up gains on Monday after the euro slipped against the dollar" following the S&P report, said Ker Chung Yang, commodity analyst for Phillip Futures in Singapore.
The euro changed hands at $1.3366 in morning Asian trade, compared with $1.3394 in late New York trade on Monday.
A stronger greenback would make dollar-priced crude less attractive to traders using other currencies such as the euro.