Israeli Prime Minister Benjamin Netanyahu warned on Tuesday that "tough sanctions" currently imposed on Iran might not be enough to prevent Tehran from obtaining a military nuclear capability.

"We need to stop Iran from acquiring nuclear weapons," he told foreign diplomats attending a reception at the presidential residence in Jerusalem, marking the 65th anniversary of the Jewish state's foundation.

"We've seen the consequences of a rogue regime having atomic weapons," he said in reference to North Korea. "Tough sanctions and talk don't always do the job."

Israel believes the Islamic republic, which has issued many bellicose statements about the Jewish state, is working to achieve a military nuclear capability and has not ruled out a military strike to prevent this happening.

Last month Iran's supreme leader Ayatollah Ali Khamenei said his country would "annihilate" the cities of Tel Aviv and Haifa if it comes under attack by Israel.

Iran denies it is developing an atomic bomb and says it needs its nuclear programme of uranium enrichment for peaceful medical and energy purposes.

Israel is widely believed to be the Middle East's sole nuclear-armed state, albeit undeclared.

At the Tuesday night reception, new Defence Minister Moshe Yaalon echoed Netanyahu's sentiments. He called Iran's nuclear programme "the most significant threat" to the world, the progress of which was proof "Tehran wasn't impressed by the steps taken so far."

"The Western states must understand that only assertive action will curb the threat. Only forcing the Iranian regime to choose between a bomb or survival will bring Iran to halt the project."

To Yaalon, while it is not the Jewish state that should spearhead efforts to prevent Iran from obtaining nuclear arms, it is Israel that could be a first target of Tehran's possible aggression.

"Israel should not lead the campaign against Iran, since it is 'only' the Little Satan," Yaalon said, using the term coined by Ayatollah Khomeini. "The Great Satan is America, or the Western world led by the US."

"But it is clear to us that the first target of the Ayatollah regime could be Israel," he said.

"The world should lead the campaign against Iran, but Israel must prepare for the possibility that it will have to defend itself on its own," Yaalon said.

Earlier on Tuesday, Israel's chief of staff, Lieutenant General Benny Gantz, said the country's military was capable of attacking Iran on its own without foreign support.

Asked in an interview on public radio if the military could wage attacks on Iran "alone" -- without the support of countries such as the United States -- Gantz replied: "Yes, absolutely."

"We have our plans and forecasts... If the time comes we'll decide" on whether to take military action, he said.

Gantz's comments echoed statements earlier this month by Netanyahu, who said Israel would "at no stage... abandon our fate into the hands of other countries, even our best friends."

In a separate interview on Tuesday, Gantz said the possibility of an Israeli strike on Iran was not imminent, and that sanctions imposed by the international community should be given priority to halt Tehran's nuclear drive.

"Iran has the means to obtain nuclear capability before the end of the year, but this does not mean it'll get there," he told news website YNet, adding that "sanctions, isolation and continued pressure" on Tehran must intensify.

Iran is estimated to have lost billions of dollars in oil sales and the value of its currency has plummeted.

An independent report in February said a fall in pharmaceutical exports to Iran was also causing harm and was undeniably triggered by international sanctions.

US President Barack Obama said in March that Iran was still more than a year away from developing a nuclear weapon.