JERUSALEM, June 6 (Reuters) - An Israeli attack on Iranian nuclear sites looks "unavoidable" given the apparent failure of sanctions to deny Tehran technology with bomb-making potential, one of Prime Minister Ehud Olmert's deputies said on Friday.

"If Iran continues with its programme for developing nuclear weapons, we will attack it. The sanctions are ineffective," Transport Minister Shaul Mofaz told the mass-circulation Yedioth Ahronoth newspaper.

"Attacking Iran, in order to stop its nuclear plans, will be unavoidable," said the former army chief who has also been defence minister.

It was the most explicit threat yet against Iran from a member of Olmert's government, which, like the Bush administration, has preferred to hint at force as a last resort should U.N. Security Council sanctions be deemed a dead end.

Iran, which denies seeking nuclear weapons, has defied Western pressure to abandon its uranium enrichment projects. The leadership in Tehran has also threatened to retaliate against Israel -- believed to have the Middle East's only atomic arsenal -- and U.S. targets in the Gulf for any attack on Iranian turf.

Mofaz also said in the interview that Iranian President Mahmoud Ahmadinejad, who has called for Israel to be wiped off the map, "would disappear before Israel does."

Mofaz's remarks came as he and several other senior members of Olmert's Kadima Party prepare for a possible run for top office should a corruption scandal force the Israeli prime minister to step down.

Iranian-born Mofaz has been a main party rival of the Israeli prime minister, particularly following the 2006 elections when Olmert was forced to hand the defence portfolio to Labour, his main coalition partner, at Mofaz's expense.

Mofaz, who is also designated as a deputy prime minister, has remained privy to Israel's defence planning. He is a member of Olmert's security cabinet and leads regular strategic coordination talks with the U.S. State Department.

Israel sent warplanes to destroy Iraq's nuclear reactor in 1981.

A similar Israeli sortie over Syria last September razed what the U.S. administration said was a nascent nuclear reactor built with North Korean help. Syria denied having any such facility.

Independent analysts have questioned, however, whether Israel's armed forces can take on Iran alone, as its nuclear sites are numerous, distant and well-fortified. (Editing by Ori Lewis and Charles Dick)