Israel's opposition leader Shaul Mofaz says an Israeli strike on Iran's nuclear sites would be ineffective without U.S. support.

Mofaz, a former military chief, spoke Saturday to Israeli TV after heightened chatter over a possible Israeli strike against Iran's nuclear program.

"Israel cannot strategically change the Iranian nuclear program," Mofaz said.

He said without U.S. support a strike would be a "disaster" that would only delay Iran's nuclear plans.

Washington has vowed military action to stop Iran from obtaining nuclear weapons but has warned Israel against acting early, insisting sanctions should be given more time.

Israel views Iran as an existential threat due to its nuclear and missile programs, support for violent anti-Israeli groups in Lebanon and Gaza as well as repeated references by Iranian leaders to Israel's destruction.