Israel's top military officer on Wednesday said it remains unclear if economic sanctions against Iran will convince Tehran to give up its nuclear program.

"The real question here is, is it sufficient enough to persuade" Iran to abandon its nuclear work and "that's to be determined," Lieutenant General Gabi Ashkenazi said after talks with his US counterpart, Admiral Mike Mullen.

"We still have some time to watch it and see what will be the final outcome," Ashkenazi told reporters at the Pentagon.

Asked how much time Israel was willing to wait, he said it would not be "appropriate" to discuss a possible deadline.

He said that Israel supported the current US-led approach focused on a fresh round of punitive sanctions.

His comments came amid apparent strain between Israel and the United States over how to confront Iran, with US officials reluctant to publicly threaten military action.

Israeli Prime Minister Benjamin Netanyahu recently told US Vice President Joe Biden that only a "credible" threat of military action would stop Iran from developing the atomic bomb, a senior Israeli official said.

But US Defense Secretary Robert Gates last week disagreed sharply when asked about Israel's view, saying the latest round of sanctions were having an impact on Iran's economy.

Mullen standing along side Ashkenazi, said that sanctions were proving more effective than some skeptics had predicted.

"I've certainly seen a body of evidence that indicates the sanctions are taking their toll, much more rapidly than some had anticipated," Mullen said.

But he said "all options remain on the table, including military options."

The United States spearheaded international efforts to impose a fourth round of UN Security Council sanctions in June, sanctions it says are aimed at bringing Iran back to the negotiating table to discuss its nuclear program.

Sanctions notably ban investments in oil, gas and petrochemicals while also targeting banks, insurance, financial transactions and shipping -- which Tehran has brushed off as having no impact.

Washington and Tel Aviv fear the atomic program masks a drive to build a nuclear bomb, but Iran denies the charge, saying its efforts are for peaceful purposes.

Gates on Tuesday warned a military strike against Iran would only delay Tehran from obtaining nuclear weapons in the short-term.