Mofaz, a former army chief, may be lining up a challenge to Olmert
A top Israeli official has said that if Iran continues with its alleged nuclear arms programme, Israel will attack it.
Speaking to Yediot Ahronot newspaper, Deputy Prime Minister Shaul Mofaz said sanctions on Iran were ineffective.
Mr Mofaz is one of three deputy prime ministers and the transport minister.
Earlier this week, Israeli Prime Minister Ehud Olmert said Iran's nuclear programme must be stopped by what he termed all possible means.
"The international community has a duty and responsibility to clarify to Iran, through drastic measures, that the repercussions of their continued pursuit of nuclear weapons will be devastating," Mr Olmert said.
Iran insists that its nuclear programme is for peaceful purposes but it is defying a demand from the UN Security Council to stop the enrichment of uranium.
"If Iran continues with its programme for developing nuclear weapons, we will attack it. The sanctions are ineffective," Mr Mofaz told Yediot Ahronot.
"Attacking Iran, in order to stop its nuclear plans, will be unavoidable," he said.
The former chief of the army and defence minister is one of several senior figures in the governing Kadima party who may challenge the leadership of Mr Olmert, who faces allegations of corruption.
The UN Security Council has approved three rounds of sanctions against Iran.
These include asset restrictions and travel bans on Iranian individuals and companies said to be involved in nuclear work.
The sanctions also ban the sale to Iran of so-called dual-use items - items which can have either a military or civilian purpose.