* Meets Kerry Wednesday to argue against easing sanctions after nuclear talks
* Netanyahu says Iran holds real power in Syria
* Saudi Arabia also worried about a deal between Washington and Iran
By Jeffrey Heller
JERUSALEM, Oct 21 (Reuters) - Israel's Benjamin Netanyahu on Wednesday will seek to dim the optimism after nuclear talks with Iran, cautioning that Tehran is strengthening its strategic regional position by calling the shots in Syria as President Bashar al-Assad's puppet master.
In talks with U.S. Secretary of State John Kerry in Rome on Wednesday, Netanyahu is expected to argue against easing Western sanctions on Iran, which hinted at recent Geneva talks it was willing to scale back its nuclear programme.
Netanyahu has long warned the West, in a message it has largely embraced, of the danger Iran would pose to the Jewish state, the Middle East and the West if it obtained nuclear arms through the programme which Iran says aims to generate power.
The right-wing prime minister will gauge just how far the United States is ready to consider any let up on sanctions imposed on Iran at the meeting with Kerry.
Reinforcing his warning of the threat of a nuclear-armed Iran, Netanyahu has added another twist to his argument, noting that Iran is behind Assad and supplies Shi'ite Muslim fighters for the civil war against Sunni rebels.
Saudi Arabia, another key U.S. ally in the Middle East, is also deeply worried about any sign of a deal between Washington and the kingdom's arch-rival, Iran.
The double-pronged message is part of Netanyahu's campaign to prevent any easing of sanctions until it actually dismantles atomic work that Israel is convinced aims to produce nuclear arms. Iran says it is enriching uranium for peaceful purposes.
Six world powers - the United States, Russia, China, Britain, France and Germany - held two days of talks with Iran in Geneva last week, the first such meetings since Iranian President Hassan Rouhani's election in June.
IRAN PLAN OFFERED HOPE
Iran offered a three-phase plan it said could yield a breakthrough in its nuclear impasse with the West, and a second round of talks is due to be held on Nov. 7 and 8 in Geneva.
"There are a lot of countries that are waiting for a signal, just waiting for a signal, to get rid of their sanctions regimes," Netanyahu told U.S. television station NBC on Sunday.
He did not name those nations, but it is a sign of Netanyahu's concern that he will fly to Rome to see Kerry, who is on a European visit.
"The focus is Iran," a senior Israeli government official said on Monday. "Clearly (Netanyahu's) top priority at the moment is the Iranian issue."
A senior State Department official, who accompanied Kerry to Europe, played down any divisions with Israel over Iran and said no decision to ease sanctions was taken at the Geneva talks.
"Any step that the United States would take would have to be - first, Iran would have to take meaningful, verifiable, transparent steps," the U.S. official said.
"That is something that obviously hasn't happened yet, and there is agreement with the Israelis that we're not going to allow Iran to acquire a nuclear weapon. That is the bottom line."
Kerry met a senior Saudi official on Monday to discuss their disagreements over Iran, Syria and Egypt as well as the surprise Saudi decision to spurn a U.N. Security Council seat.
Netanyahu has alluded in a series of public addresses to the irony of Arab countries effectively closing ranks with Israel in their concern over a nuclear-armed Iran and the strategic influence the Shi'ite nation already wields in the region.
The West, Netanyahu has said, must be particularly wary of any accommodation with Iran that would bolster its regional influence further after its activities in Syria.
In Netanyahu's words, "Syria has become an Iranian protectorate", much like the Hamas-ruled Gaza Strip and southern Lebanon, where the Iranian-backed Hezbollah guerrilla group holds sway.
What Netanyahu hears at his meeting with Kerry could help to determine whether Israel, backed by the powerful American Israel Public Affairs Committee (AIPAC) lobbying group, will opt to turn to its traditional allies in the U.S. Congress to press President Barack Obama to stand tough on Iran.
So far, there have been no rumblings among Israeli officials that Netanyahu will go that route. Some Republican legislators are already calling for tougher sanctions against Iran.
And officials close to Netanyahu, avoiding any public dissonance with the Obama administration, declined to comment on a New York Times report on Thursday that Washington is weighing a slow release of frozen Iranian assets if Tehran takes specific steps to curb its nuclear programme.
Obama's credibility among Israelis took a hit last month when he backed off striking Syria, seemingly going against a pledge to attack if Damascus deployed chemical weapons.
Two thirds of Israelis now doubt Obama will keep his promise to prevent Iran from developing nuclear weapons, according to this month's "Peace Index", an opinion poll published by Tel Aviv University and the Israel Democracy Institute.
Netanyahu has hinted that his country, widely believed to be the Middle East's only nuclear power, may act on its own to prevent Iran from building a bomb, although its military ability to accomplish that has been publicly questioned by former Israeli security chiefs. (Additional reporting by Arshad Mohammed in Paris; Editing by Peter Millership)