Israel rejected a UN resolution calling for a ceasefire in Gaza yesterday and jets and tanks again pounded the Palestinian enclave.
Israeli Prime Minister Ehud Olmert dismissed Thursday's binding Security Council resolution demanding an "immediate and durable" ceasefire as "unworkable".
Diplomats sounded the alarm that Egyptian-brokered truce talks launched this week might also be foundering.
Israel's security Cabinet debated for the second time in three days whether to send in reservists for a push into the Gaza Strip's towns and cities. There was no word on the outcome.
Mark Regev, Mr Olmert's spokesman, declined to say whether the ministers had decided to expand the ground operation.
"I can't go into operational details. The military pressure on Hamas will continue," Mr Regev said, adding that the Islamist group had fired 30 rockets into Israel yesterday.
Mr Olmert said earlier: "The firing of rockets this morning only goes to show that the UN decision is unworkable and will not be adhered to by the murderous Palestinian organisations".
The United States, which abstained in the UN vote, offered further public support for Israel's military goals.
"This situation will not improve until Hamas stops lobbing rockets into Israel," White House spokesman Scott Stanzel said.
He also said President George W. Bush had voiced his concern to Mr Olmert about the humanitarian situation and the loss of civilian lives during the Israeli assault on the Gaza Strip.
Israel's air force said it hit over 50 targets overnight. As fighting on the ground went on through the day, Palestinian medics counted at least 19 dead, including civilians.
Israeli planes bombed the outskirts of Gaza City, residents said. Tanks shelled a house in Beit Lahiya in the north of the strip, killing six Palestinians from one family, medics said.
A UN agency said in a report that 30 Palestinians were killed earlier this week when the Israeli army herded dozens of civilians into a house which was later hit by shells.
Hamas officials say they are weighing the UN resolution, but have voiced irritation they were not consulted. One official said a Hamas delegation from Damascus is going to Cairo today to respond to the Egyptian ceasefire proposal.
Hamas wants any ceasefire deal to include the ending of Israel's crippling economic blockade of the Gaza Strip and the withdrawal of all Israeli forces from the territory.
Israel's key demands are for a complete halt to Hamas rocket fire and for international guarantees to stop the Islamist group rearming via smuggling tunnels under the border with Egypt.