Gold may rise for a sixth straight week on speculation a slowing American economy will erode the value of the dollar, increasing the appeal of the precious metal as an alternative investment.

Some 79% of the 28 traders, investors, and analysts surveyed by Bloomberg News from Sydney to Chicago on November 9 and November 10 advised buying gold, which rose 90 cents last week to $630.10 an ounce in New York. The percentage predicting a gain was the highest in the survey since April 2004. Four respondents said to sell, and two were neutral.

Gold has rallied 9.2% since October 6 as the dollar slumped to a two-month low against the world’s major currencies. The U.S. Labor Department this week probably will report a decline in producer prices and a deceleration in consumer costs, spurring speculation the Federal Reserve may trim interest rates to boost the economy, eroding the value of the dollar.

“The Fed can potentially move quicker to reduce rates as inflationary pressures recede,” the director of metals research in London at Calyon Corporate & Investment Bank, Michael Widmer, said. “This means that downward pressure on the dollar should persist, which is positive for gold.”

Gold futures on the Comex division of the New York Mercantile Exchange have climbed 21% this year. Last week’s gain was predicted by a majority of analysts surveyed on November 2 and November 3. The Bloomberg survey has forecast prices accurately in 81 of 133 weeks, or 61% of the time.

American economic growth slowed in the third quarter to the slowest pace since 2003 as the housing market slumped and the trade deficit widened.

The Fed Bank of New York’s general economic index this week may show manufacturing in New York state slowed this month to 15 from 22.9 last month, according to the median of 29 estimates in a Bloomberg News survey. A number greater than zero signals most manufacturers reported business is improving.

“The weakness in the dollar is the major support for gold at the moment,” the head of research at Geojit Financial Services Ltd. in Mumbai, Alex Mathews, said.”The U.S. currency is likely to fall further, propping gold up.”

The producer-price index probably fell 0.4% last month from a year earlier, according to the economists in a Bloomberg survey. The consumer-price index probably rose 1.6% from a year earlier, slowing from a 2.1% gain in September, another Bloomberg survey showed. The government is scheduled to release the producer-price report tomorrow and the consumer data on November 16.

“Weak-dollar psychology should help next week,” a partner at commodity research firm Logic Advisors LLC in Upper Saddle River, New Jersey, William O’Neill, said. Gold “broke to the upside technically with funds back in a big way,” he said.

Gold climbed above its 200-day moving average on November 1.

The Fed has maintained a 5.25% target for overnight loans between banks since August, after raising rates 17 times since June 2004 to curb inflation. Interest-rate futures show a 34% likelihood of a rate cut to 5% in March, up from an 11% chance on November 3.

The European Central Bank president, Jean-Claude Trichet, and the Bank of Japan governor, Toshihiko Fukui, suggested last week they will raise rates, boosting the appeal of their currencies.

Demand for StreetTracks Gold Trust, an exchange-traded fund that is linked to the price of gold and traded in New York, has risen 5.4% this month. The fund has 132.7 million shares outstanding, each representing a 10th of an ounce of gold.

“A weaker tone in the dollar and rising investment interest in exchange-traded fund gold” will help prices, an analyst at Kanetsu Asset Management in Tokyo, Kegeyama Tatsuo, said.

The precious metal will reach $650 an ounce, Mr. Tatsuo said.

Gold also may rise on speculation China’s central bank will diversify reserves away from the dollar into gold, traders and analysts said.

“I’m still very bullish on gold,” the head of IL &FS Investsmart Commodities Ltd. in Mumbai, Suni Ramrakhiani, said.”We may see a further rally in the metal with central banks across the world selling dollars and increasing gold in their reserves. We’ve seen that sentiment being already expressed by China.”

The People’s Bank of China governo, Zhou Xiaochuan, said last week the central bank will “stick to the existing policy” of diversifying its foreign-exchange reserves, the world’s biggest at about $1 trillion, because of “safety, efficiency, and liquidity.”

Gold will rise to $650 an ounce, Mr. Ramrakhiani and Kanetsu Asset Management’s Mr. Tatsuo said. Mr. Mathews of Geojit Financial Services predicted $645.