GAZA CITY, Gaza Strip - Israel, under international pressure, is considering a 48-hour halt to its punishing four-day air campaign on Hamas targets in Gaza to see if Palestinian militants will stop their rocket attacks on southern Israel, Israeli officials said Tuesday.
  
Any offer would be coupled with a threat to send in ground troops if the rocket fire continues.

Prime Minister Ehud Olmert discussed the proposal -- floated by France's foreign minister -- and other possible next steps with his foreign and defence ministers, Israeli officials said, speaking on condition of anonymity because they were not supposed to make the information public.

U.S. President George W. Bush and U.S. Secretary of State Condoleezza Rice called leaders in the Middle East to press for a durable solution beyond any immediate truce.
  
And members of the Quartet of world powers trying to promote Mideast peace concluded a conference call with an appeal for an immediate ceasefire. The Quartet powers are the United States, the United Nations, the European Union and Russia.

The European Union itself late Tuesday also urged an immediate truce and for Israel to reopen borders to allow vital supplies to reach Gazans. The Paris statement by the 27-member bloc avoided blaming either side for the current fighting.

In its Tuesday night meeting, Israel's leadership trio stepped up preparations for a ground offensive, conducting a telephone survey among cabinet ministers on a plan to call up an additional 2,500 reserve soldiers, if required. Earlier this week, the cabinet authorized a callup of 6,700 soldiers.

After the four-hour meeting, Olmert's office issued a statement early Wednesday saying no details of the discussion would be made public because of the sensitivity of the subject matter.

Amid talk of a truce, Israeli warplanes continued to unload bombs on targets in Gaza. Powerful airstrikes caused Gaza City's high-rise apartment buildings to sway and showered streets with broken glass and pulverized concrete.

Israel's ground forces on Gaza's border also used artillery for the first time.

Israel's military said it hit 31 targets on Tuesday, including a cabinet building, rocket-launching sites, and places were missiles were being built. Some of the hits on sites with weapons stockpiles triggered secondary explosions.

After nightfall, Israel destroyed 40 tunnels under the sealed Gaza-Egypt border in another attempt to cut the vital lifeline that supplies Gaza with both commercial goods and weapons for Hamas and other militant groups.

Hamas kept up its rocket barrages, which have killed four Israelis since the weekend, and sent many more running for bomb shelters -- some in cities under threat of attack for the first time, as the range of the rockets grows.

A medium-range rocket hit the city of Beersheba for the first time ever, zooming 45 kilometres deep into Israel and slamming into an empty kindergarten. A second rocket landed in an open area near the desert city, Israel's fifth-largest.

The military said later it successfully struck the group that launched those rockets.

A pattern of daytime lulls and nighttime spikes in rocket fire appeared to be emerging as militants found safer launch cover in darkness.

Four days into a campaign that has killed 374 Palestinians and prompted Arab and international condemnation, a diplomatic push to end the fighting gathered pace.

In two phone calls to Defence Minister Ehud Barak on Monday and Tuesday, French Foreign Minister Bernard Kouchner appealed to him to consider a truce to allow time for humanitarian relief supplies to enter the beleaguered Gaza Strip, two senior officials in Barak's office said.

Foreign Minister Tzipi Livni was expected to travel Thursday to Paris for talks with French President Nicolas Sarkozy, who has put his growing international stature to use in other conflict zones, most recently to help halt fighting between Russia and Georgia in August.

Israeli media reported that Sarkozy would also travel to Jerusalem Monday for talks with the Israeli and Palestinian leaders.

A Hamas spokesman said any halt to militant rocket and mortar fire would require an end to Israel's crippling blockade of the Gaza Strip. "If they halt the aggression and the blockade, then Hamas will study these suggestions," said Mushir Masri.

Egypt, which has been blockading Gaza from its southern end, has come under pressure from the rest of the Arab world to reopen its border with the territory because of the Israeli campaign.

Egypt has pried open the border to let in some of Gaza's wounded and to allow some humanitarian supplies into the territory. But it quickly sealed the border when Gazans tried to push through forcefully.

In a televised speech Tuesday, Egyptian President Hosni Mubarak responded to critics, including the leader of the Lebanese militia Hezbollah, who have accused him of collaborating with Israel.

"We tell anybody who seeks political profits on the account of the Palestinian people: The Palestinian blood is not cheap," he said, describing such comments as "exploiting the blood of the Palestinians."

Mubarak said his country would not throw open the border crossing unless Palestinian President Mahmoud Abbas -- a Hamas rival -- regains control of the border post.

Mubarak has been rattled by the presence of a neighbouring Islamic ministate in Gaza, fearing it would fuel more Islamic dissidence in Egypt.