* U.S. optimism over fiscal deal boosts markets
* European shares climb, U.S. stocks gain
* Euro gains vs dollar; oil prices edge up
NEW YORK, Nov 29 (Reuters) - A benchmark world stock index climbed to a three-week high and commodities gained on Thursday amid optimism that U.S. political leaders were progressing toward a deal to avoid a fiscal crisis that could derail growth in the world's biggest economy.
The "fiscal cliff" - automatic spending cuts and tax increases that come into effect in 2013 unless Congress agrees on an alternative - is the biggest risk facing global markets in the final weeks of the year, following an agreement earlier this week on fresh aid for Greece.
U.S. benchmark indexes followed European markets higher, with an added boost after data on Thursday showed weekly initial jobless claims fell for a second consecutive week, and that the economy grew faster than initially thought in the third quarter.
The reports suggested that the world's largest economy was on a stable path to recovery. A separate report showed the National Association of Realtors monthly index of pending sales of existing U.S. homes rose 5.2 percent in October.
"There will be a deal before December 31 to avert the economy facing disaster," said Peter Cardillo, chief market economist at Rockwell Global Capital in New York.
"We're back on track for a year-end rally to continue," he said.
The growing optimism spread across world share markets, sending the MSCI global equities index up 0.9 percent to its highest since Nov. 7.
The Dow Jones industrial average was up 64.20 points, or 0.49 percent, at 13,049.31. The Standard & Poor's 500 Index was up 8.14 points, or 0.58 percent, at 1,418.07. The Nasdaq Composite Index was up 21.20 points, or 0.71 percent, at 3,012.98.
The FTSE Eurofirst 300 index rose 0.9 percent.
Commodity markets also got some support from hopes for a U.S. fiscal pact. Crude oil futures rose $2.06 to $88.53 a barrel, and Brent climbed $1.63 to $111.13 a barrel.
The euro was up 0.46 percent at $1.3004.