Not long after US elections, and just weeks before Israelis went to the polls, persistent rocket fire from Gaza pushed Israel into a major air campaign which evolved into a ground operation.

Sound familiar?

That was the scenario almost four years ago when Israel launched what turned out to be a devastating 22-day operation in Gaza, which cost the lives of 1,400 Palestinians -- half of them civilians -- and 13 Israelis, 10 of them soldiers.

On Wednesday, eight days after the US presidential vote and with Israel gearing up for a January 22 general election, the Jewish state embarked on another major air campaign in Gaza in a bid to stamp out rocket fire.

The latest campaign has so far claimed the lives of more than 100 Palestinians.

In the same period, militants have fired nearly 700 rockets over the border, killing three Israelis and for the first time hitting Tel Aviv and Jerusalem, sparking warnings from Prime Minister Benjamin Netanyahu that he was preparing to expand the campaign.

All the signs point to preparations for a ground operation, with the army sealing all roads around Gaza and some 40,000 reservists reportedly massed along the border, awaiting orders from the political echelon.

Dan Harel, former deputy chief of the Israeli military, said there was a maximum of 48 hours for Egyptian-led truce efforts to bear fruit or the troops would have to go in.

"There are two basic alternatives," he told journalists in a Monday evening conference call.

"One is an agreement, cooked in Cairo, and the other is escalating the situation and moving forward into the Gaza Strip with a land effort, which is going to be bad for both sides," he said in English. "We are about 24 to 48 hours from this junction."

Military analyst Reuven Pedatzur told AFP on Monday that "a ground incursion would be a disaster."

"What would they be aiming at doing? Reconquering the Strip? How long would they be there? There are no defined goals.

"Israel is now waiting for something to happen to be able to say, 'Okay, we won, now we can stop'" without embarking upon a ground operation, he said.

But Israel's hand could be forced if a significant number of its citizens are killed by rockets -- even though political leaders have no appetite for going in, he said.

"Nobody wants an incursion, that's the absurdity of the situation," said Pedatzur who directs the Centre for Strategic Dialogue at Netanya College.

If it did come to putting boots on the ground, it would be very different from Cast Lead, Yossi Yehoshua wrote in top-selling newspaper Yediot Aharonot.

"A ground incursion will not be a repeat of Operation Cast Lead" because militants in Gaza "have learned the lessons," he said.

Hamas and Islamic Jihad have "increased the quantity of rockets, they learned how to better use the weapons they received from Iran, and mainly -- they've changed their deployment against the Israeli army."

And if four years ago, Israeli forces entered only after massive shelling took out most of the rocket launch sites, things are different now, he said.

"The troops who will have to go in will have to go in a lot deeper, and the risk to their lives will be much greater.

"This time it will not end with 10 killed," Yehoshua wrote, referring to the number of soldiers killed in Cast Lead.

A senior Israeli officer told AFP there were "many" differences between the current situation and the lead-up to Cast Lead.

"At the military level, (Hamas) capabilities today are far richer than they used to be," he said.

"A lot of weapons are flowing from Libya, from Iran, from Sudan," he said.

But Israel has also improved its standing since the end of Cast Lead in mid-January 2009, the officer said.

"We conduct our business in a more professional way, this is what we used the time for," he said.

Writing in the left-leaning Haaretz newspaper, military commentator Amos Harel said Israel's abilities to launch more accurate air strikes had improved.

"The aerial firepower that Israel is employing is much more accurate and less destructive than that used in Israel's last major operation in Gaza," he said.