Copper fell to a two-week low as Goldman Sachs Group Inc. forecast more losses.

Goldman said prices will probably drop another 16 percent by the end of next year and expects Chinese demand to grow at the slowest pace in almost two decades. The Bloomberg Commodity Index fell 0.5 percent, a 13-year low.

“The recent down moves have been more extreme than the up moves,” Nic Brown, the head of commodity research at Natixis SA in London, said by phone. “Sentiment remains negative and prices will keep pushing lower.”

Copper futures for September delivery declined 0.4 percent to $2.418 a pound by 10:27 a.m. on the Comex in New York. Prices fell to a six-year low of $2.381 on July 8 and are down 14 percent this year. On the London Metal Exchange, the metal for delivery in three months lost 0.4 percent to $5,340 a metric ton ($2.42 a pound).

Expectations that the Federal Reserve will soon raise interest rates has strengthened the dollar, making raw materials priced in greenbacks more expensive for buyers in other currencies. The Bloomberg commodities gauge slid 26 percent over the past year on concern demand is slowing in top user China.

Goldman on Wednesday lowered its copper-price outlook by as much as 44 percent through 2018, and expects the metal to reach $4,500 by the end of 2016. China’s economy is growing at the slowest pace in 25 years, according to economist estimates compiled by Bloomberg.

The number of requests to withdraw copper from LME warehouses relative to global inventories dropped to the lowest since March 2013. That suggests consumer appetite is waning and indicates inventories may rise further. Stockpiles are at the highest since May 6, bourse data show.

On the LME, aluminum, lead, zinc and nickel fell, while tin gained.