NEW YORK (AP) Copper and other industrial metals rose July 21 on signs of strong demand and expectations for growth in China, sending copper to its highest level in three weeks.

Copper for September delivery rose 9.15 cents, or 3 percent, to settle at $3.0930 a pound, its highest close since June 29.

Adam Klopfenstein, senior market strategist at Lind-Waldock, said it was unclear if copper prices would be able to stay above $3 a pound as the strength of the economic recovery remained uncertain.

Federal Reserve Chairman Ben Bernanke sounded caution about the economic recovery in testimony before Congress July 21. Bernanke said the economic outlook remains “unusually uncertain,” and the central bank was considering options to help revive the recovery if it faltered.

Industrial metals such as copper are used in manufacturing and construction. Strong economic growth would mean more production at factories and more building, boosting demand for the metal and its production.

Tom Pawlicki, commodities analyst with MF Global Research in Chicago, said higher expectations for growth in China was driving copper’s gains. On July 20, the International Energy Agency said China had surpassed the United States to become the world’s biggest energy consumer.

Copper producer Freeport-McMoRan Copper & Gold Inc. said July 21 that global copper demand was robust despite the bumpy economic recovery. The company was planning to restart some operations stopped during the recession.

The copper market was strong in northern Europe, China and in the United States, said CEO Richard Adkerson.