JERUSALEM, May 29 (Reuters) - To ask Israeli officials how the border with a future Palestine should look is to invite a deluge of data -- from the regional military balance, to topographical surveys, to intelligence projections on Hamas strength.

But no one will map it out. For while Prime Minister Benjamin Netanyahu has refused any return to the "indefensible" lines held before the West Bank's occupation in the 1967 war, the Israelis themselves have no ready alternative to hand.

The issue was at the centre of a White House spat last week between Netanyahu and U.S. President Barack Obama, who in an unprecedented step proposed publicly the 1967 boundaries serve as the basis for delineating the Palestinian state.

"Is there some kind of borders chart that can be whipped out and presented now? No," said Yosef Kuperwasser, a former chief military intelligence analyst who now serves as director-general of Israel's Strategic Affairs Ministry.

Such planning, he argued, is impossible given the nebulous menaces of a Middle East in upheaval and of the Palestinian polity, which has balked at Netanyahu's peacemaking terms that include recognition of Israel as a Jewish state.

"We can't have a map until we know what the solutions will be, in terms of both strategic security and the philosophical security of being assured that the Palestinians have ceased to be even a prospective source of hostility," Kupperwasser said.

The Netanyahu government's sequencing promises to bedevil U.S. peace mediation that seeks to set borders before other core disputes -- such as Jerusalem's status and the future of Palestinian refugees -- are tackled.

Palestinians, and Netanyahu's domestic critics, see in his rejection of the pre-1967 lines a right-wing legerdemain designed to scrap draft territorial deals of previous Israeli governments and prepare for sweeping West Bank annexations.

While Israel's hope of keeping swathes of its West Bank settlements under an accord would appear to have been met by U.S. and Palestinian calls for "mutually agreed swaps" of land, this falls far short of satisfying Netanyahu's defence doctrine.

Like his predecessors, Netanyahu insists the Palestinian state be demilitarised and that Israel have free access to its airspace and control of sensitive communications frequencies.

EYES EAST

The worst-case scenario posited by Netanyahu advisers and confidants for the post-withdrawal West Bank, meanwhile, recalls the pan-Arab mobilisations in 1967 against a fledgling Israel just 10 miles (16 km) wide at its coastal heartland:

Once U.S. forces leave Iraq, it could close ranks with Iran and send tanks toward Israel; the buffer offered by Jordan might not hold, especially if revolutions seen in Egypt and Tunisia reach Amman; the West Bank would risk becoming a springboard for Palestinian militants, bolstered by Arab armies as well as the Hezbollah and Hamas guerrillas to Israel's north and south.

More immediately, Israel's commercial hub of Tel Aviv and nearby Ben-Gurion Airport, its international gateway, could be paralysed should Palestinian rocket and mortar crews have the run of the West Bank highlands overlooking them.

"Israel cannot base itself on a snapshot of reality in 2011," said Dore Gold, a former Israeli ambassador to the United Nations who accompanied Netanyahu to Washington as a consultant. "No one can guarantee, for Israel, which regimes to the east will be in power in five years' time."

Past Palestinian land offers to Israel had amounted to single-figure percentages of the West Bank -- enough, Gold said, to take in settlements but not to ensure national security.

How much might that require? Gold, like Kupperwasser and other officials, would not be drawn on figures. But he said Israel would be hard put to compensate the Palestinians. "You would have to carve out from the living flesh of Israel -- roads, kibbutzim, military bases," he said.

Shaul Arieli, a centre-left peace activist who in the late 1990s served as a military consultant under first-term premier Netanyahu, said Israeli negotiators' maps then called for a 40 percent West Bank annexation.

That has likely been pared down to between 15 percent and 20 percent due to Netanyahu's current openness to keeping a minimal Israeli military garrison in the Jordan Valley, Arieli said:

"In any event, Israel does not have land that it can give up in exchange for anything more than a 3 percent swap."

Though few dispute the region's volatility, Netanyahu's views are challenged by experts who say they play down Israel's military primacy and the corrosion caused to its demographics and international legitimacy by remaining mired over Palestine.

"Any border the political echelon sets as the State of Israel's border is a border that the Israel Defence Forces would be capable of defending," said Dan Halutz, a former military chief now aligned with the centrist opposition party Kadima.

"Of course I wouldn't rule out that we must prepare for the possibility of tanks being lined up on the border, but the kind of wars being waged in recent years do not have a territorial dimension as much as an aerial one," he told Israeli television.

Military historian Martin van Creveld credited Israel's current containment of Hezbollah, Hamas and Syria to its superior arms and said these could be brought to bear in turning the kidney-shaped West Bank into a "noose" for any Arab invader.

"It is crystal-clear that Israel can easily afford to give up the West Bank," he wrote in the Jewish Daily Forward.

"Strategically speaking, the risk of doing so is negligible. What is not negligible is the demographic, social, cultural and political challenge" of maintaining the West Bank occupation.