NEW YORK (MarketWatch) -- Gold futures rose Friday for a fourth-straight session, briefly topping the $960-an-ounce mark for the first time in nearly two months as the U.S. dollar weakened against its major rivals on concerns over U.S. credit ratings.

Gold for June delivery rose to as high as $963.10 an ounce in early morning trading, topping $960 for the first time since March 19. It was last up $6.30, or 0.7%, to $957.50 on the Comex division of the New York Mercantile Exchange. The metal is set to end the week up nearly 3%.

The greenback fell Friday to the lowest level in four months against the euro as worries increased that the U.S. could lose its triple-A credit rating.

Standard & Poor's Ratings Service Thursday warned Britain that it may lose its triple-A rating, triggering a drop in U.K. bonds and sparking global fears about sovereign credit ratings. In the U.S., 10-year Treasury bonds fell below a crucial level.

A weaker greenback makes dollar-denominated commodities such as oil and gold less expensive to holders of other currencies. Those countries tend to bid up oil prices.

Some investors also buy gold as a hedge against a weaker dollar and inflation.

"The gold price is predominantly driven by the dollar weakness at the moment," said analysts led by Barbara Lambrecht at CommerzBank. "As long as the dollar remains on the back foot, gold should continue to rise."

The weaker dollar also boosted other commodities Thursday, with crude-oil futures up more than 1% to above $61 a barrel.

In exchange-traded funds, holdings in the Gold SPDR Trust /quotes/comstock/13*!gld/quotes/nls/gld (GLD 94.32, +0.47, +0.50%) , the biggest gold ETF, stood at 1,105.62 metric tons Thursday, unchanged for a seventh-straight session, according to latest data from the fund.

In other metals trading Friday, July copper rose 6.4 cents, or 3.1%, to $2.115 a pound.

July silver gained 28 cents, or 1.9%, to $14.725 an ounce. The June palladium contract rose 65 cents, or 0.3%, to $236.10 an ounce, while July platinum gained $2.40, or 0.2%, to $1,157.10 an ounce.

Moming Zhou is a MarketWatch reporter based in New York.