As the scope of Israel's 'Operation Pillar of Defence' was widened to a broader range of targets, increasing the risk of collateral damage, US President Barack Obama offered strong support for Israeli's right to defend itself.
But he demanded ceasefire talks to prevent a "ramping up" of fighting and said it would be "preferable" for Israel to avoid a military thrust into the densely populated Gaza Strip.
"We're actively working with all parties in the region to see if we can end those missiles being fired without further escalation of violence in the region," he said. "If this can be accomplished without a ramping up of military activity in Gaza, that is preferable."
William Hague, the Foreign Secretary, said that he and David Cameron had warned the government of Benjamin Netanyahu that "a ground invasion of Gaza would lose Israel a lot of the international support".
His comments drew an immediate rebuke from Moshe Ya'alon, a former general and Israel's Vice Prime Minister, who said Israel demanded more support when it was confronting a threat looming over one-fifth of its 5.5 million population.
"We expect our allies to support us as we use all the tools available in order to defend our people," he said. "To say the least, we don't like these types of reservations being expressed."
But Mr Ya'alon acknowledged that Hamas, the Palestinian group that controls Gaza, was looking to Cairo for help in brokering a ceasefire. He said Israel was ready for a ceasefire if "we see the opportunity on both sides".
Meanwhile, Laurent Fabius, the French foreign minister, visited Israel to offer his country's help toward forging an "immediate ceasefire".
Mr Netanyahu said he was preparing for co-ordinated diplomatic efforts. "I will continue to consult with world leaders," he said. "I appreciate the understanding they are showing for the right of Israel to defend itself. I have emphasised in these conversations the effort Israel does to avoid harming civilians."
But he aimed to keep up the verbal pressure on Hamas, threatening that his forces were ready to invade at short notice.
"The army is prepared to significantly expand the operation," he said.
Mark Regev, the prime minister's spokesman said diplomatic efforts were under way "in parallel" with the military operation.
Gaza militants, meanwhile, launched dozens of rockets into Israel and targeted its commercial capital, Tel Aviv, for a fourth day with one attack in the morning and another after nightfall.
Israel's "Iron Dome" missile shield shot down all three rockets, but falling debris from the daytime interception hit a car, which caught fire.
Israeli officials said more than 900 rockets had been fired at Israel since the operation was launched last Wednesday with a missile strike that killed Ahmed al-Jaabari, the head of Hamas's military wing.
In scenes recalling Israel's 2008-2009 winter invasion of Gaza, tanks, artillery and infantry massed in field encampments along the sandy, fenced-off border. Military convoys moved on roads in the area newly closed to civilian traffic, while 30,000 reservists have been called up.
Col Richard Kemp, a former British army commander who toured the troop encampments on Saturday, said that the massing forces had already strengthened Israel's position.
The apparent imminence of a ground invasion ignited a debate across the political spectrum.
Leaders of communities nearer the border affected by the rocket attacks issued a joint statement demanding the government conclude the military operation by wiping out the militants rocket stocks.
Ehud Yaari, an Israeli analyst for Channel Two television, wrote in 'Foreign Policy' magazine: " Egypt faces a choice: launching a high-level political dialogue with the Israel to obtain the ceasefire that it desires, or seeing the continuation of violence in Gaza." (© Daily Telegraph, London)