The Israel Defense Forces on early Sunday began mobilizing tanks and reinforcing ground troops near the Gaza border, in preparation for a possible ground incursion.
Defense Minister Ehud Barak told Sky News that he would not rule out widening the offensive in the Gaza Strip to include a ground invasion.
Barak on Saturday also said Israel "cannot really accept" a cease-fire with Hamas, rejecting calls by the United Nations and the European Union for a truce after Israel Air Force strikes killed at least 230 people in Gaza.
"For us to be asked to have a cease-fire with Hamas is like asking you to have a cease-fire with Al-Qaida," Barak said in an interview with Fox News. "It's something we cannot really accept."
Asked whether Israel would follow up the air strikes with a ground offensive, Barak said, "If boots on the ground will be needed, they will be there."
"Our intention is to totally change the rules of the game," he said.
Prime Minister Ehud Olmert earlier on Saturday said no country in the world would put up with the rocket and missile strikes Israel suffers from and that the time had come to react.
Olmert's words came during a press conference he held hours after the Israel Defense Forces and the IAF carried out attacks in Gaza that Palestinian officials said left at least 230 dead and hundreds wounded.
"Israel has done all it could to preserve the cease-fire with Hamas, but our desire for quiet was met with terror," Olmert said.
Olmert added that Israel "is not itching for a fight, but will not back down from one either."
The Prime Minister also vowed to restore quiet to the lives of Israel's southern residents, adding that they "will not be abandoned." He also said that the IDF operations in Gaza would take time, and asked for patience.
Leader of the Hamas government in the Gaza Strip, Ismail Haniyeh, accused Israel on Saturday of a "massacre" of Palestinians, saying "Palestine has never witnessed an uglier massacre."
Haniyeh's statement was broadcast by his Islamist group's Gaza-based television channel, Al-Aqsa.
Earlier Saturday, Barak held a press conference on Saturday in which he said had no choice and that "the time has come to fight."
Barak said the IDF and IAF attacks had destroyed "terrorism infrastructure" and hit more than 150 Hamas targets. He also said the current campaign would be widened and will continue for some time.
Barak said Israel cannot stand by while rockets strike the communities of the western Negev and "won't let terror hurt our citizens or soldiers."
Foreign Minister Tzipi Livni on Saturday addressed the ongoing IDF campaign in Gaza, saying, "Until now we have shown restraint. But today there is no other option than a military operation."
Livni, speaking in English at a press conference, said Israel had no choice but to act to "protect our citizens from attack through a military response against the terror infrastructure in Gaza."
Livni called the IDF operations an expression of Israel's "basic right to self-defense."
The Foreign Minister laid blame for the bloodshed at the feet of Hamas, saying the group "cynically abuses its own civilian population and their suffering for propaganda purposes."
Palestinians in the Hamas-ruled Gaza Strip fired at least 54 Qassam and Grad rockets into southern Israel on Saturday after the IDF campaign began. One of the rockets directly struck a home in the town of Netivot, leaving one Israel dead and four with moderate to serious injuries.
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