UNDATED (AP) - Oil prices rose to around US$81 a barrel Friday as the U.S. dollar weakened, making dollar-based commodities cheaper for investors with other currencies.

By early afternoon in Europe, benchmark crude for May delivery was up 56 cents to US$81.09 a barrel in electronic trading on the New York Mercantile Exchange. The contract fell 8 cents to settle at US$80.53 on Thursday.

The euro rose to US$1.3372 on Friday from US$1.3277 on Thursday.

"Crude oil prices rose ... as the decision from European Union to provide a fiscal aid package to Greece spread economic optimism across the energy market and boosted investors' sentiment for risk appetite," said a report from Sucden Financial Research in London. "It seems that there is a strong support at the US$80 per barrel area."