Signs were growing Monday that Israel is preparing to unleash a major ground offensive against the Gaza Strip as airstrikes pounded Palestinian targets and army and naval guns shelled the densely populated coastal strip on Israel's southern border.

The English-language Times of Israel website reported that Israeli Prime Minister Binyamin Netanyahu, Defense Minister Ehud Barak and far-right Foreign Minister Avigdor Lieberman have approved expanding airstrikes and preparations for an invasion of the Hamas-ruled territory.

This followed reports that Egyptian-mediated negotiations Sunday between Israel and Hamas, with both sides communicating through Cairo, to halt the 6-day-old war collapsed even though they reportedly came close to a deal at one point.

"With the breakdown in talks, it is possible the Israeli government has decided to widen its offensive in Gaza and try to attain the goals of its operation," U.S. global security consultancy Stratfor observed.

There's been no indication on the ground that a major invasion is imminent but Netanyahu's government has authorized the mobilization of up to 75,000 reservists. Thousands, along with armor and artillery, massed on the border with Gaza over the weekend.

The mobilization numbers far exceed the 20,000-strong force used in Israel's December 2008 invasion of Gaza, Operation Cast Lead.

That could indicate a much larger force is planned this time but the 75,000 troops, on top of regular forces, is probably is intended to cover other possible contingencies, such as the Iranian-backed Hezbollah in Lebanon, on Israel's northern border, launching operations to support the Palestinians.

That's unlikely at this time, as Hezbollah is widely believed to have sent fighters to Syria to help the embattled regime of President Bashar Assad battle rebel forces.

Also, the Syrian war has sent political tensions in Lebanon soaring, with Hezbollah unsettled because it could lose its longtime patron and arms supplier in Damascus, cutting it off from Tehran.

There has been speculation that the Israelis plan to send their armor-led ground forces into Gaza on Tuesday.

The 2008 invasion was preceded by five or six days of relentless airstrikes to soften Hamas' defenses, and that would seem to be what the Israeli air force has been doing since last Wednesday, when the fighting flared.

The Israelis have flown more than 1,000 airstrikes as part of Operation Pillar of Defense in that period, attacking in excess of 500 targets. These included Hamas rocket sites, depots, command centers and government buildings, as well as assassinating several key Hamas military leaders from the air.

Heavy artillery fire from the guns being massed along the Gaza border would likely signal an invasion was only hours away.

On the other side, Hamas, outnumbered and outgunned, is using the only offensive weapon it has, apart from suicide bombings: its arsenal of Iranian-made Fajr-3 and Fajr-5 unguided missiles, smuggled in through underground tunnels from Egypt's Sinai Peninsula.

Until it obtained these missiles in any numbers it could only fire off short-range Soviet-era Grad rockets and home-made Qassams.

Although the Fajr's range is around 50 miles, it puts the urban and industrial sprawl around Tel Aviv, with a population of around 3 million, and even Jerusalem, holy to Muslims, Jews and Christians, in the cross hairs for the first time.

That allowed Hamas to punch way above its weight but it was a red line for Israel because within the parameters of its conflict with Hamas the Fajr became a strategic weapon for the Palestinians.

Even fired singly or in small clusters, rather than in large battlefield broadsides, against Israeli cities, which apart from some Scud-Bs fired on Tel Aviv by Saddam Hussein during the 1991 Gulf War, have never been bombarded, their psychological and political impact far outweighs their military value.

With Israeli elections scheduled for January, hitting Tel Aviv provides further motivation at a time when pro-Western Arab regimes have fallen, boosting support for Hamas.

The big question is how many Fajrs Hamas has.

Since the missiles are 20 feet long and weigh 2,000 pounds it's difficult to conceive Hamas was able to smuggle in more than a few dozen along with Iranian-trained crews.

There are reports Hamas has stripped some Fajrs of their 300-pound warheads to give them extra range just to spread alarm and despondency.