Oil fell below $114 a barrel to a one-month low on Tuesday as an inconclusive Italian election result revived investor concern about instability in the euro zone and weaker fuel demand growth.

The uncertainty in Rome, along with concerns the United States may rein in its economic stimulus and soft manufacturing data from China, is clouding the global economic outlook and could erode oil's modest price gain so far this year.

Brent crude hit a session low of $113.00, its weakest since Jan. 28, and was down $1.07 at $113.37 by 1238 GMT. U.S. oil slipped 71 cents to $92.40, after touching a low of $91.92 earlier, a level not seen since Jan. 4.

"The main driver now is the deadlock after the Italian election - it's triggered risk-off sentiment in the financial markets," said Carsten Fritsch, senior oil analyst at Commerzbank in Frankfurt.

Other commodities such as copper also fell, the euro hit its lowest in nearly seven weeks before recovering, and European shares slid, led by bank stocks.

The result confirmed fears Italian politicians would not be able to form a government strong enough to carry out effective reforms, reviving memories of the financial crisis that took the 17-member currency block to the brink of collapse in 2011.

Brent rallied to a nine-month high near $120 in early February but has since fallen back on signs the global economy remains fragile.

Also on investors' radar are talks between major powers and Iran over Tehran's nuclear programme. World powers were expected to offer Iran limited sanctions relief on Tuesday if it agrees to halt its most sensitive nuclear work.

Few believe the meeting on Tuesday and Wednesday in the Kazakh city of Almaty will yield an immediate breakthrough. Still, a reduction in tensions could weigh on oil prices.

"The risk premium in Brent prices could still ease if there is any hope of a closer cooperation between Iran and the UN Security council," said Andrey Kryuchenkov, analyst at VTB Capital.

On the technical charts, Brent has support at $113 a barrel and $110 should prices fall further, Kryuchenkov said. So far on Tuesday, support at $113 has held.

Prices could come under further pressure should stockpiles of crude in the United States rise, as expected, for a sixth straight week. Analysts polled by Reuters expect stocks to rise by 2.3 million barrels.

There was also growing concern among investors the Federal Reserve could ease up on its bond-buying programme sooner than expected. Fed Chairman Ben Bernanke's congressional testimony later in the day will be scrutinised for clues. (Addtional reporting by Manolo Serapio Jr. and Manash Goswami in Singapore; Editing by Anthony Barker)