* U.S. sugar sets new three-year top (Updates with settlement values throughout)
By Barani Krishnan
NEW YORK, July 30 (Reuters) - Renewed optimism about economic recovery sent commodity prices rallying again on Thursday after a two-day sell-off, with soybeans leading the surge with a 7-percent rise.
The 19-commodity Reuters-Jefferies CRB index rose to a one-month high, settling up 4 percent. It recouped all that it lost between Tuesday and Wednesday as agricultural, energy and metals markets reacted to a weakening in the dollar and upbeat economic data out the United States, Europe and China.
"It's a classic case of commodities leaping on the first sign of the dollar's weakening," said Ralph Preston, analyst at HeritageWestFutures.com in San Diego, California.
"But the economy is still a wild card and I'm not convinced our troubles are going away yet. That's probably why we're not seeing any price stability at this moment, whether it's for crude oil, copper or gold."
U.S. crude oil for September delivery settled up 6 percent at $66.94 a barrel, after topping $67 in earlier trade.
Benchmark copper in New York finished up 3.5 percent at $2.5640 a lb.
U.S. gold futures closed almost 1 percent higher at $934.90 an ounce.
The dollar -- which reverted earlier this week to the safe-haven status it enjoyed at the height of the financial crisis -- fell as investors' appetite for risk grew on seeing government data showing a drop in the number of Americans on jobless benefits.
Optimism from the stock market also crossed over into commodities after strong quarterly earnings at some major U.S. firms and solid demand for the U.S. Treasury Department's auction of a record $28 billion of 7-year notes.
Investors were emboldened by data showing euro zone economic sentiment at its highest in eight months, and a pledge by China's central bank to keep a loose monetary policy to consolidate its economic recovery.
In the case of soybeans, aggressive buying by China of U.S. soybeans sent prices for futures traded on the Chicago Board of Trade to three-week highs.
The U.S. Department of Agriculture said China bought 1.9 million tonnes, with 1.8 million set to be delivered in the new-crop (2009/10) marketing year, beginning Sept. 1. The balance of 120,000 tonnes were for shipment this marketing year.
It was the biggest single sale of soybeans made to China since 2.24 million tonnes were announced sold just over a year ago, according to USDA data.
Even without the latest round of Chinese buying, U.S. soybean supplies already had been forecast by the USDA to fall to 32-year lows.
"China is still buying beans and bean supplies will be tight for the next 30 to 45 days," said Paul Haugens, vice president for grains broker Newedge USA.
CBOT's benchmark soy contract for August settled up 70-3/4 cents at $11.28-1/4 a bushel, after a session high at 11.34-1/4 a bushel.
U.S. raw sugar futures for October finished up 1 percent at a new 3-year high of 18.75 cents per lb. (Editing by Christian Wiessner)
