Two attacks in as many days in the West Bank have cast an even deeper pall over direct Palestinian-Israeli negotiations that already seem crippled from the start.

In comments that preceded a “working dinner” among negotiators last night, four Middle Eastern heads of state implored Benjamin Netanyahu, the Israeli prime minister, and Mahmoud Abbas, the president of the Palestinian Authority, to seize what many see as a final, fleeting opportunity to secure a so-far elusive two-state solution to the Middle East conflict.

Even Barack Obama, the US president, whose tireless urging brought the Palestinian and Israeli leaders together for the first time in 20 months, acknowledged the profound negotiating difficulties ahead.

In a press conference before the dinner, the American president said last night: “I know these talks have been greeted in some quarters with scepticism. We are under no illusions.

“But we know that the status quo is unsustainable – for Israelis, for Palestinians, for the region and for the world. It is in the national interests of all involved, including the United States, that this conflict be brought to a peaceful conclusion.”

This week’s events seemed a harbinger of those apprehensions. On Tuesday, four Jewish settlers were shot dead near the West Bank town of Hebron. Yesterday, as negotiators convened in Washington, Palestinian gunmen injured two Israelis in a similar-style drive-by shooting.

Hamas, which controls the Gaza Strip, claimed responsibility for both attacks.

In mentioning the shootings last night, Mr Netanyahu used his time at the White House podium to remind his Arab counterparts that “peace must be met with security”.

“We don’t seek a brief interlude between two wars. We don’t seek a temporary respite between outbursts of terror. We seek a peace that will end the conflict between us once and for all,” said the Israeli premier. “We seek a peace that will last for generations.”

Mr Netanyahu’s comments also touched upon one of his more frequent arguments: that peace brings with it the potential for Palestinian economic development. The Israeli prime minister reminded reporters of the West Bank’s recent high level of economic growth – which touched 8.5 per cent last year, according to the International Monetary Fund – as well as that region’s confident strides toward improving government institutions.

“I see what a period of calm has created for the Palestinian cities of Ramallah, of Jenin and throughout the West Bank: a great economic boom,” said Mr Netanyahu.

“We want the skyline of the West Bank to be dominated by apartment towers, not missiles. We want the roads of the West Bank to flow with commerce, not terrorists.”

But for all of Mr Netanyahu’s soaring rhetoric, his comments avoided direct mention of settlement building in the West Bank – an issue that, even more than the recent terror attacks, forms the negotiation’s most salient talking point

Mr Abbas and his negotiating team have threatened to walk out of the talks if Mr Netanyahu allows a ten-month moratorium on new settlement construction in the West Bank to expire on September 26.

Mr Netanyahu has said that extending the settlement freeze would almost certainly destroy his right-wing parliamentary coalition, ending his premiership.

For his part, Mr Abbas broached the settlements question head-on. The Israelis, like the Palestinians, must abide by their “obligations” to the peace process that include continuing the freeze on new settlements, he said.

Indeed, in the run-up to this week’s direct talks, the question of Israeli settlement expansion has eclipsed other final status considerations, such as the status of Jerusalem and the rights of Palestinians refugees to return to their homelands.

As the intransigence on both sides has persisted, many analysts have accused the Israelis of profiting from the impasse by expanding their presence in the West Bank.

Rashid Khalili, an Arab Studies professor at Columbia University who, in a telephone interview last night, called the latest negotiations a “delusion for the foolish and inattentive”, said: “The process ... certainly hasn’t produced peace. It’s produced a quadrupling of the settlement population.”

Still others have drawn a more direct connection between the drawn-out negotiations and the recent violence against settlers. Ghassan Khatib, a former government minister and the director of the Palestinian Government Media Centre, said that while Mr Netanyahu and others have used security concerns as a pretext to justify Israel’s occupation and settlement of Palestinian land, the continued Israeli presence only begets more violence.

“All of the violence that is taking place is happening within the context of occupation. And that the Israeli occupiers have been all along violent and the Palestinians have been sometimes violent in their attempts to end that occupation,” Mr Khatib said, referring to the attacks yesterday and the day before. “So the only way to get rid of violence is to get rid of occupation.”