Gold headed for the longest weekly rally since March as U.S. economic data backed the case for sustained monetary stimulus. Russia and Kazakhstan added bullion to reserves for a ninth month in June.

Spot gold gained as much as 0.3 percent to $1,338.50 an ounce, and traded at $1,334.55 at 8:30 a.m. in Singapore. Prices are 3 percent higher this week after advancing to a one-month high of $1,348.65 on July 24. Volumes for Shanghai’s benchmark spot bullion contract climbed to a one-week high of 14,618 kilograms yesterday.

Gold is up 8.1 percent in July, heading for the best month since January 2012, as the Bloomberg Dollar Index retreated 1.5 percent after Federal Reserve Chairman Ben S. Bernanke said it’s too early to decide whether to begin scaling back bond purchases in September. Data this week showed sales of new U.S. homes rose in June to a five-year high while claims for jobless benefits increased. Central banks including Russia and Kazakhstan increased gold reserves in June, International Monetary Fund data showed.

“Gold advanced on expectations that the Fed will maintain stimulus measures after U.S. jobless claims rose more than expected,” Lachlan Shaw, an analyst at Commonwealth Bank of Australia (CBA), wrote in an e-mail today.

Gold for December delivery increased as much as 0.5 percent to $1,336.10 an ounce on the Comex in New York, before trading at $1,334.80, also set for a third week of gains.

Silver for immediate delivery climbed as much as 0.5 percent to $20.3595 an ounce before trading at $20.2877, heading for a weekly gain. The metal has risen 3.2 percent in July, set for the first monthly increase since January.

Spot platinum was little changed at $1,449.70 an ounce, poised to advance for a third week and also heading for the first monthly gain since January. Palladium added 0.1 percent to $739.80 an ounce to trim the first weekly loss in a month.