A senior official says that a meeting by five world powers on Iran's nuclear program has been canceled due to China's opposition.

The U.S., Russia, China, Britain, France and Germany had planned to meet Friday. The official from one of the five world powers demanded anonymity Monday because his information was confidential.

The meeting was to be in Brussels or on the sidelines of the Copenhagen summit.

Iran has shrugged off three sets of U.N. Security Council sanctions imposed to curb its uranium enrichment program. Tehran says it needs to enrich to make fuel for a future reactor network. But the program can also be used to make fissile warhead material.

Israel's defense minister urged the world Monday to agree to tough new sanctions on Iran, suggesting that military strikes remained a final option should Tehran refuse to heed Security Council demands.