Less than two days after it thought it had persuaded Israel and the Palestinians to halt their fighting, the US was last night frantically trying to prevent a slide back into widespread conflict.
All afternoon and into the night, the hills outside the city of Nablus, in the West Bank, looked more like the Wild West, albeit with some indisputably modern elements.
Palestinian gunmen traded fire with Israeli soldiers, while Jewish settlers, trapped behind rocks and shrubs, tried desperately to stay out of the line of fire, some of them simultaneously updating Israel television stations from their mobile phones. Above them, Israeli assault helicopters clattered, drawing Palestinian fire and shooting down to quell it, so that the soldiers could lead the settlers out of the warzone.
After dark, Israel reported that one man had been killed, a rabbi in his 60s, and at least three injured. The Palestinians also reported one fatality, a man in his 30s. And, as ever, each side accused the other of starting the conflict, and of breaching the ceasefire understandings, as mediated by the US and others at Sharm al-Sheikh on Tuesday.
Fearing a resurgence today of wider clashes, US officials, including leading CIA officers, were last night making frantic phone calls to try and persuade the two sides to give another chance to the attempts at a truce.
The battle began in early afternoon, when a group of 37 settlers, including women, children and two babies, began an army-escorted tour in the Mount Ebal area outside Nablus - in flagrant breach of an order, higher up the army chain of command and evidently ignored lower down, barring such excursions at these times of high anxiety.
The Palestinian claim is that the settlers entered "Area A" - territory that is under full Palestinian control, and opened fire. "They shot at a Palestinian car," said Mr Amin Makboul, head of the local Tanzim paramilitary fighters, whose gunmen were involved in the clashes.
The Israeli claim is that the settlers were fired upon for no reason. "We were no threat to anyone," said one of the group, Mr Yoel Neumann, last night.
Throughout the afternoon, the gunfire continued, and the army battled to extricate the wounded. Later last night, Palestinians were fleeing eastern Nablus, fearful of Israeli reprisal attacks.
Two more Palestinians died yesterday, in even more hotly-disputed circumstances. An explosion ripped through the Bethlehem headquarters of Palestinian Authority President Yasser Arafat's Force 17 bodyguard unit, killing two of his policemen and injuring several others. Both sides were agreed that Israel had nothing to do with this, but there the consensus ended.
Israeli sources said this was a "work accident" - the premature explosion of a bomb, which was being prepared for use against Israel. Mr Arafat was furious about it, the Israeli sources said, and had ordered wholesale personnel changes as a consequence.
Palestinian officials, however, spoke variously of gas cylinders exploding, or of a blast in an ammunition store, which contained explosive material seized from Islamic militants.
Today, of course, is Friday again - always the most tense day of the week, with the focus, as ever, on the disputed Temple Mount, the Haram al-Sharif, in Jerusalem. Israel is again planning to bar Palestinian men under 40 from entering Jerusalem to pray at the mosques there, in an effort to avoid another day of bloodshed.
Tomorrow, Mr Arafat will join Arab heads of state at the Arab Summit in Cairo, where he intends to demand a freezing of Arab normalisation with Israel, and the reviving of the trade boycott of Israel.
The White House National Security Adviser, Mr Sandy Berger, yesterday called on Israel and the Palestinians to stand by the agreement, saying the gruesome alternative was "playing out before their eyes."