* Novices, naysayers among Israeli PM's inner council
* Ex-official says forum needs 3 months to study Iran
By Dan Williams
JERUSALEM, March 19 (Reuters) - Israeli Prime Minister Benjamin Netanyahu has streamlined his security cabinet but its crop of untested politicians and a member who has rankled at sabre-rattling could hamper any decision to strike Iran.
The seven-minister forum was unveiled on Monday as part of a new centre-right government whose "paramount task", Netanyahu said, is to "stop Iran from arming itself with nuclear weapons".
At less than half the size of the previous security cabinet, this one includes two novice ministers, Yair Lapid and Naftali Bennett. A third member, Gilad Erdan, has political pedigree but has never previously been part of the key decision making circle.
Casting an informed vote on Iran "will require these newcomers study the material for at least three months", said a retired security official from Netanyahu's previous government.
The Iranian issue, Netanyahu said, will top the agenda of his talks with U.S. President Barack Obama, who begins a visit to Israel, the occupied West Bank and Jordan on Wednesday.
Acknowledging that a unilateral attack on Iran's distant and well-defended nuclear facilities would pose an unprecedented strain for Israel's military, the ex-official added: "It might be better were this security cabinet to learn the ropes on a smaller-scale operation, say in Syria or in Gaza, beforehand."
Under Israeli law, war must be approved by the full cabinet. But the security cabinet, whose secrecy is better enforced, can green-light more limited military "missions". Making that distinction depends on whether Israel's intelligence chiefs anticipate an escalation into protracted conflict.
In a U.N. speech last September, Netanyahu set a mid-2013 "red line" for Iranian uranium enrichment which has bomb-making potential although Tehran says it is peaceful. But Iran's slowdown in the stockpiling of medium-enriched uranium could push that line further into the future.
The pared-down security cabinet suggests Netanyahu may rely on it rather than form a parallel, informal council of senior ministers like he did in his previous term. Israeli officials gave no indication a new such advisory group was in the works.
Netanyahu enjoys a hawkish majority in both cabinets, especially now that loyalist Moshe Yaalon has taken over as defence minister from Ehud Barak, a centre-left maverick.
Still, Netanyahu's strategy could stumble over centrist Lapid, his main coalition partner. Lapid argues that Israel, widely believed to be the Middle East's only nuclear-armed nation, should use force against Iran only as a last resort and lobby world powers to curb its atomic programme.
Among those apparently informing Lapid's views is Meir Dagan, a retired Mossad spymaster who ridiculed Netanyahu for talking up a war option that could alienate Israel's Western allies and invite bloody reprisals by Iran, Islamist guerrillas in Lebanon and Gaza, and possibly Syria.
"I meet with (Dagan) all of the time," Lapid told Reuters. Asked to elaborate, he said: "No, sorry. It's between us."
Another centrist and possible naysayer in the security cabinet is Tzipi Livni. While foreign minister in 2007, she was quoted by Israeli media as saying a nuclear-armed Iran would not threaten the Jewish state's existence.
Campaigning against Netanyahu last year, Livni lambasted his likening of the Islamic Republic to Nazi Germany. A Livni spokeswoman had no immediate comment on the minister's past remarks, describing her current position on Iran as "moderate".
Less so is Bennett, a far-right former high-tech entrepreneur and ex-commando. At a foreign policy debate before the Jan. 22 election, Bennett was asked whether he would support an attack on Iran.
"I don't know enough," he said. "I don't have the information but everything is preferable to a nuclear Iran, which would make Israel the most dangerous place in the world for Jews." (Additional reporting by Crispian Balmer; Writing by Dan Williams; Editing by Jeffrey Heller and Alison Williams)