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JERUSALEM — A U.S.-brokered cease-fire has gone up in a puff of smoke.

Far from giving any substance to the truce that was declared in mid-June, Israel and the Palestinian Authority have become mired in a pattern of attack and counter-attack — or, more bluntly, revenge and more revenge.

On Wednesday, Israel augmented its forces around Palestinian cities in the West Bank in response to a Palestinian mortar attack a day earlier on Jerusalem's Gilo neighborhood — the first time Palestinians have fired mortars from the West Bank, or at Jerusalem, since their violent uprising began nearly 10 months ago.

As troop and tank reinforcements took up positions Wednesday, Prime Minister Ariel Sharon denied the move was part of a plan to "reconquer" areas under Palestinian Authority control.

Additional soldiers arrived at existing West Bank checkpoints early Wednesday. Others took up positions along roads, stopping and searching passing cars. No figures were available on the exact size of the buildup.

For their part, Palestinian officials said Tuesday's attack on Gilo came in retaliation for an Israeli helicopter attack earlier in the day that killed four Palestinians, including several leading Hamas militants, in the West Bank city of Bethlehem.

Israeli military officials said the helicopter attack targeted a Hamas leader who was planning to bomb the closing ceremonies of the Maccabiah Games on Sunday.

Tuesday's helicopter assault also came in retribution for a terror attack on Monday, when a Palestinian suicide bomber killed two Israeli soldiers in the coastal town of Binyamina.

The Binyamina attack, for which Islamic Jihad claimed responsibility, prompted Israeli tanks to shell Palestinian military posts late Monday near the West Bank city of Jenin.

With each new assault, statements from each side provide little reason to hope that the season of action and reaction will end soon.

Israel's police chief, Shlomo Aharonishky, warned Tuesday of more attempted terror attacks by Islamic militants. Also Tuesday, Islamic Jihad militants vowed to continue attacking Israel, despite a purported warning from Palestinian Authority President Yasser Arafat to halt attacks inside Israel's pre1967 border.

Watching as the cease-fire they brokered becomes increasingly meaningless, U.S. officials were reduced to repeating a familiar mantra — calling on the Palestinian Authority to bring to justice those responsible for terror bombings, and urging the Israeli government to show restraint in the face of such attacks.

"There can be no military solution to this conflict," State Department spokesman Richard Boucher said.

It was not the first time Boucher has offered this opinion, and it was not the first time it went unheeded.

Recent days have seen increased diplomatic efforts aimed at ending the Israeli-Palestinian violence — but they all have failed.

Following Monday's terror attack in Binyamina, Prime Minister Ariel Sharon's communications adviser, Ra'anan Gissin, told Army Radio the suicide bombing was a slap in the face from Arafat, who had met a day earlier in Cairo with Foreign Minister Shimon Peres.

After Sunday's meeting, which lasted more than an hour, Peres said he had told Arafat that Israel is waiting for seven days of complete calm before starting peace moves.

But ensuing events provided little reason to believe there would be calm, or anything close, anytime soon.

Just hours after the Peres-Arafat meeting, two Palestinians were killed late Sunday night while preparing a bomb near a Jerusalem stadium where the Maccabiah Games were due to open the next day.

And on Monday, in some of the fiercest fighting since the Palestinian uprising began last September, Israeli tanks moved into Palestinian-controlled parts of Hebron and exchanged heavy fire with Palestinian gunmen.

During the firefight, Israel destroyed four police posts operated by the Force 17 presidential guard and wounded nine people before withdrawing.

Israel said its incursion came in response to heavy shooting by Palestinian gunmen at Israeli troops and civilians in the volatile West Bank city.

The Peres-Arafat meeting came on the heels of talks last week in Ramallah between Arafat and Sharon's son, Omri.

Sharon's oft-declared stance that he will not negotiate while Palestinian violence continues was turned against him by right-wing ministers who criticized the premier for letting Peres meet with Arafat.

Sharon defended the Cairo meeting — as he had defended a previous Peres-Arafat encounter in Lisbon last month — by saying the foreign minister had not engaged in negotiations, but had reiterated Israel's demand for an end to violence, terror and incitement.

Peres' meeting with Arafat "dealt with one issue: an end to terror and return of security for Israeli citizens," Sharon said Monday. "In this area, I think we can make every effort."