Barely two months ago, the Palestinian Authority President, Mr Yasser Arafat, and the Israeli Prime Minister, Mr Ehud Barak, were wrestling semi-playfully with each other as they entered two weeks of intensive talks in the US to try and reach a new peace accord.
Barely two weeks ago, Mr Arafat was a guest at Mr Barak's home in Israel, and although they didn't discuss issues of real substance, the atmosphere between them was easygoing, even friendly. Now, Mr Arafat is accusing Mr Barak of massacring the Palestinians. And Mr Barak claims that Mr Arafat has proved he is no "partner for peace".
Mr Arafat has the backing of the United Nations Security Council, which approved a resolution in the early hours of yesterday morning condemning Israel's "excessive use of force against Palestinians". Of the 80-plus fatalities in 11 days of conflict, almost all have been Palestinians; Israel has used assault helicopters, firing air-to-ground missiles, among other weaponry, in countering crowds of Palestinian protesters armed with rocks, petrol bombs and, in their midst, gunmen with automatic weapons. The US, which routinely vetoes UN resolutions critical of Israel, abstained.
Mr Barak, who asserts that Mr Arafat need only give "a clear order" to halt the protests, is even backed in this belief by many on the firm left of the Israeli political spectrum, members of the "Peace Camp" such as Meretz Knesset member, Mr Ran Cohen, who are expressing disillusion with the Palestinian leader and dismay that years of attempted reconciliation are falling apart.
The source of this breakdown, unmistakably, was the effort to find an agreed solution to the disputed status of the Temple Mount (as Jews call it) or Haram al-Sharif (as Muslims refer to it) - the hilltop in the heart of Jerusalem's Old City where Mr Barak knows many, perhaps most, Israelis cannot conceive of relinquishing sovereignty, and where Mr Arafat knows that the Arab world cannot be reconciled to anything other than Muslim control.
And the consequence of the breakdown could well now be nothing less than regional war. President Hosni Mubarak of Egypt, whose country made peace with Israel more than 20 years ago, warned for weeks that Israel and the Palestinians would be more prudent if they sought to sign another "framework" peace treaty, rather than attempting the near-impossible by tackling the Temple Mount problem.
Now Mr Mubarak is facing a mounting tide of demonstrations by his own Islamists, and sending quiet messages to Mr Barak that Egypt cannot stay on the sidelines indefinitely while the killing of Palestinians goes on.
Still, publicly at least, Mr Mubarak is calling for "wisdom" from his fellow Arab leaders - in contrast to the offers of military support for the Palestinians coming from Yemen and Libya.
Jordan's inexperienced King Abdullah, so anxious to mollify his own majority Palestinian population that he had himself photographed giving blood for Palestinian wounded last week, has issued a ban on all demonstrations after his forces killed a Palestinian in clashes. His late father's peace treaty with Israel on 1994 was never happily accepted by the Jordanian populace, and is now an acute embarrassment. In both these countries, a severing of relations grows more likely with every Palestinian fatality.
Lebanon is on alert for war - its forces mobilised in anticipation of Israeli attack. Israel has reinforced its troop deployment on the northern border, following Saturday's kidnapping there of three Israeli soldiers by Hizbullah. Mr Barak says he holds Syria ultimately responsible for their fate; Syria, under its inexperienced President Bashar Asad, says it will "not bend" to Israel's threats. Twenty-seven years ago, the Middle East went to war on the Day of Atonement, Yom Kippur, the most solomn day in the Jewish calendar. Today is Yom Kippur.