Israeli Defence Minister Ehud Barak said Friday the world must quickly stop Iran from reaching the point where even a ‘surgical’ military strike could not block it from obtaining nuclear weapons.

Amid fears that Israel is nearing a decision to attack Iran's nuclear programme, Barak said tougher international sanctions are needed against Teheran's oil and banks so that "we all will know early enough whether the Iranians are ready to give up their nuclear weapons program."

Iran insists its atomic programme is aimed only at producing energy and research, but it has refused to consider giving up its ability to enrich uranium.

The United Nations has imposed four rounds of sanctions against Iran, but veto-wielding Russia and China say they see no need for additional punitive measures. That has left the US and the European Union to try to pressure other countries to follow their lead and impose even tougher sanctions.

"We are determined to prevent Iran from turning nuclear. And even the American president and opinion leaders have said that no option should be removed from the table and Iran should be blocked from turning nuclear," Barak told reporters during the annual meeting of the World Economic Forum.

"It seems to us to be urgent, because the Iranians are deliberately drifting into what we call an immunity zone where practically no surgical operation could block them," he said.

But while Barak called it "a challenge for the whole world" to prevent a nuclear-armed Iran, he stopped short of confirming any action that could further stoke Washington's concern about a possible Israeli military strike.

Iran has accused Israel of masterminding the killing of Iranian scientists involved in the nuclear program, but Barak declined to comment on that.

Earlier, he told a panel discussion that "a stable world order" is incompatible with a nuclear-armed Iran because countries such as Saudi Arabia, Turkey and Egypt will all want the bomb.

"This will be the end of any nonproliferation regime," Barak said. "The major powers in the region will all feel compelled to turn nuclear."

Separately, UN Secretary General Ban Ki-Moon urged a resumption of dialogue between Western powers and Iran on the nuclear issue.

He said on Friday that Teheran must comply with Security Council resolutions and prove conclusively that its nuclear programme is not directed at making arms.

"The onus is on Iran," Ban said at a press conference. "They have to prove themselves that their nuclear development programme is genuinely for peaceful purposes, which they have not done yet."

Ban expressed concern about the most recent report of the International Atomic Energy Agency (IAEA), which strongly suggested Iran's nuclear program has a military purpose.

On Thursday, President Mahmoud Ahmadinejad said Iran is ready to revive talks with the US and other world powers but suggested that Teheran's foes will have to make compromises to prevent negotiations from again collapsing in stalemate.

Iran says it won't give up its right to enrich uranium and produce nuclear fuel, but it has offered to allow IAEA inspectors to visit its nuclear sites to ensure that the programme won't be weaponized.

IAEA chief Yukiya Amano said at a Davos session that "we do not have that much confidence if Iran has declared everything" and its best information "indicates that Iran has engaged in activities relevant to nuclear explosive devices."

"For now they do not have the capacity to manufacture the fuel," he said. "But in the future, we don't know."

Amano added that an IAEA mission would be sent Saturday to address this issue.

"If the enrichment to higher levels is in a declared facility, we can find it very quickly," he said. "The problem is we do not know if these are all the declared facilities."

Richard Haass, a former top US diplomat who heads the Council on Foreign Relations, said international law justifies a pre-emptive strike only to stave off an "imminent" attack.

"The real question is can Iran assure us what it is not doing?" he said.

Israeli defence officials said Friday that new European sanctions on Iran could constrain Israel. They said any Israeli strike against Iranian nuclear facilities may lack international legitimacy while the world waits to see the effects of the new measures.

The officials spoke on Friday on condition of anonymity because they weren't authorized to discuss sensitive military matters.

Much of the West agrees with Israel that Iran, despite its denials, is developing nuclear weapons technology. But the United States clearly worries that a military attack could backfire, by dividing international opposition to Iran - and send oil prices skyrocketing.

Israel has attacked nuclear sites in foreign countries before. In 1981, Israeli warplanes destroyed an unfinished Iraqi nuclear reactor. In 2007, Israeli aircraft destroyed a site in Syria that the UN nuclear watchdog deemed to be a secretly built nuclear reactor.

But Israel is unlikely to strike without coordinating with the Americans, who maintain forces on aircraft carriers and military bases in the Gulf.

In spite of his tough words to Iran, Ban said that dialogue among the "three-plus-three" - Germany, France and Britain plus Russia, China and the United States - is the path forward.

"There is no other alternative for addressing this crisis than peaceful ... resolution through dialogue," said Ban.

Ban noted that there have been a total of five Security Council resolutions so far on the Iranian nuclear programme, four calling for sanctions.

It's not just the West that is concerned.

"We take it for granted Iran would want nuclear weapons," Yan Xuetong, dean of the Institute of Modern International Studies at Tsinghua University, said of China. "Certainly, China is working very hard with the international community to prevent this."