World stocks were set to end the year up almost 13 percent on Monday but uncertainty loomed as U.S. politicians prepared for last-minute talks to avoid a fiscal crunch of spending cuts and tax hikes that could drag down the world economy in 2013.

In Washington, the two political parties are set to hold further talks later to try and avoid the $600 billion "fiscal cliff" kicking in from the start of January and which if left unchecked, would wipe around 4 percent off U.S. GDP.