"Instead of caring about the people of Gaza, Hamas decided to use Gaza to use rockets to kill innocent Israelis," Bush told reporters after a White House meeting with a Sudanese official. "Israel's obviously decided to protect itself."
"Any cease-fire must have the conditions in it so that Hamas does not use Gaza as a place from which to launch rockets," Bush added.
Bush said Secretary of State Condoleezza Rice had briefed him earlier on Monday on the Gaza situation.
"The United States is concerned about the humanitarian crisis. We care about the people of Gaza and therefore have provided millions of dollars of fresh aid to the United Nations to help," he said.
"All of us of course would like to see violence stop," Bush said, but added that the cessation should not come at the expense of steps needed to prevent a Gaza crisis from recurring.
Bush spoke in the Oval Office as Israeli tanks, planes and ground forces pounded Gaza and Israel's defense minister said the offensive against Hamas militants in the Palestinian enclave would go on until Israel was safe.
International efforts to secure a cease-fire moved ahead with French President Nicolas Sarkozy and Middle East special envoy Tony Blair visiting the region, but they had no apparent immediate impact on the fighting.
The death toll in besieged Gaza rose to at least 541 people over the 10-day offensive.
The Bush administration has supported Israel, saying Hamas must halt rocket fire at Israel for a truce to take shape.
