Oil prices fell slightly Tuesday as investors awaited the results of the U.S. presidential election.

Benchmark oil for December delivery was down 6 cents to $85.59 per barrel at late afternoon Bangkok time in electronic trading on the New York Mercantile Exchange. The contract rose 79 cents to finish at $85.65 a barrel on the Nymex on Monday.

Brent crude, which is used to price international varieties of oil, fell 25 cents to $107.48 on the ICE Futures exchange in London.

President Barack Obama is fighting for re-election in an extremely tight race with Republican challenger Mitt Romney. The uncertain outcome of the race for leader of the world's biggest economy has kept trading on financial and commodities markets muted this week.

The economic crisis in Greece is another factor that traders must weigh. The Greek parliament holds a critical vote this week on a new, four-year austerity package that will impose further wage and benefit cuts.

Unions opposed to more austerity measures have called for a 48-hour general strike. Police are bracing for violence in the debt-ridden country, now entering its sixth year of recession.

Lawmakers are expected to pass the measure. If not, Greece could lose vital rescue loans that have kept it afloat since May 2010 — raising the threat of bankruptcy and a euro exit.

"It's a big week this week, with the U.S. election and the situation in Greece in particular. So there is the potential for volatility," said Ric Spooner, chief market analyst at CMC Markets in Sydney.

In other energy futures trading in New York:

— Wholesale gasoline rose 0.4 cent to $2.624 per gallon;

— Heating oil fell 0.8 cent to $2.975 per gallon;

— Natural gas fell 2.7 cents to $3.527 per 1,000 cubic feet.