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By Dan Williams

JERUSALEM, Sept 28 (Reuters) - Israel has received an advanced U.S.-made radar, staffed by American personnel, as part of preparations to fend off any future ballistic missile attack by Iran, officials involved in the deployment said on Sunday.

The arrival of the X-band radar is a gauge of the depth of defence ties between Israel and the United States. But by cementing Israel's technical dependency on its ally, it may boost Washington's power to veto unilateral Israeli action aimed at denying Iran access to nuclear weapons.

The X-band was stationed this month at Nevatim military base in southern Israel, which regularly hosts joint Israeli-U.S. air defence drills, officials said. The radar came with a long-term American garrison which Israel Radio put at some 120 personnel.

"This is a major upgrade in bilateral preparations for the threats facing Israel," said an official, who declined to be identified by name or nationality. Asked to elaborate on the threats, the official pointed to Iran and Syria.

Built by Raytheon Co <RTN.N>, the X-band system has been described by U.S. officials as capable of tracking an object the size of a baseball from about 2,900 miles (4,700 km) away.

It would let Israel's Arrow II ballistic shield engage an Iranian Shehab-3 missile about halfway through what would be its 11-minute flight to Israel.

U.S. PACKAGE

Israeli Defence Minister Ehud Barak secured the Pentagon's agreement to supply the X-band during July talks. The Americans also said they would increase Israel's access to their Defence Support Programme (DSP) satellites, which spot missile launches.

In parallel, the allies are together improving the Arrow shield, which fires interceptors to knock out incoming missiles at high altitude.

Noting the American focus on counter-measures, one official familiar with the deal said it was compensation for reluctance on the part of the Bush administration to support Israeli preparations for a possible attack on Iran.

"Barak wanted the whole package, defensive and offensive, but what he got from (U.S. Secretary of Defence Robert) Gates was just the defensive stuff," the official said.

The United States has been leading efforts to curb Iran's atomic ambitions through sanctions, mindful of threats by Israel -- assumed to have the Middle East's only nuclear arsenal -- to resort to military strikes if it deems diplomacy a dead end.

Iran, which denies seeking the bomb but whose President Mahmoud Ahmadinejad has stirred war fears by calling for the Jewish state to be "wiped off the map", has vowed to respond to an attack with missile launches on Israel and U.S. assets in the Gulf. The X-band could help Israel fend off such retaliation.

Addressing foreign journalists and diplomats this month, Amos Gilad, a senior Barak adviser, played down the extent of U.S. leverage in curbing Israeli unilateralism vis-a-vis Iran.

"We are an independent state," he said. "We have to take our (own) decisions."

(Additional reporting by Ari Rabinovitch, Editing by Mark Trevelyan)

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