Gold jumped the most in four weeks after Dagong Global Credit Rating Co. cut its credit rating for the U.S. and on speculation the Federal Reserve will postpone slowing stimulus. Dagong cut the local and foreign currency credit ratings of the U.S. today to “A-” from “A.”

“There was a knee-jerk reaction to the Chinese downgrading,” said David Wilson, an analyst at Citigroup Inc. in London, which estimated about 10 million ounces of gold and 16 million ounces of silver traded after the report. “When the ultimate worry is about the dollar, maybe you go to gold.”

Gold for immediate delivery climbed as much as 3 percent to $1,321.38 an ounce, the most since Sept. 18. Futures trading volume was 77 percent above average for the past 100 days for this time of day, data compiled by Bloomberg showed.