Israeli Prime Minister Benjamin Netanyahu vowed Wednesday to press ahead with a fierce military offensive in the Gaza Strip, pushing back against calls from the United States to wind down the operation that has left hundreds dead.

Netanyahu's tough comments marked the first public rift between the two close allies since the fighting began last week and could complicate international efforts to reach a cease-fire. His pushback also plunges the pair into a difficult early test of the U.S.-Israel relationship.

Israel continued to pound Hamas targets in Gaza with airstrikes, while Palestinian militants bombarded Israel with rocket fire throughout the day. In another sign of potential escalation, militants in Lebanon fired a rocket barrage into northern Israel.

After a visit to military headquarters, Netanyahu said he appreciated “the support of the American president,” but he said Israel would push ahead to return “calm and security” to Israeli citizens.

He said he was “determined to continue this operation until its aim is met.”

He spoke shortly after U.S. President Joe Biden told Netanyahu that he expected "a significant de-escalation today on the path to a cease-fire,” the White House said.

Biden had previously avoided pressing Israel more directly and publicly for a cease-fire with Gaza's Hamas militant rulers. But pressure has been building for Biden to intervene more forcefully as other diplomatic efforts gather strength.

Egyptian negotiators have also been working to halt the fighting, and an Egyptian diplomat said top officials were waiting for Israel’s response to a cease-fire offer. The diplomat spoke on condition of anonymity in line with regulations.

Moussa Abu Marzouk, a top Hamas official, told the Lebanese station Mayadeen TV that he expected a cease-fire in a day or two.

Meanwhile, German Foreign Minister Heiko Maas said he would fly to the region Thursday for talks with Israelis and Palestinians.

Israel’s Foreign Ministry said the foreign ministers of Slovakia and the Czech Republic would join him after being invited “to express their solidarity and support” for Israel.

Earlier in the day, the Israeli military said it was widening its strikes on militant targets in southern Gaza to blunt continuing rocket fire from Hamas. At least nine people were killed Wednesday in the Gaza Strip.

The current round of fighting between Israel and Hamas began May 10, when the militant group fired long-range rockets toward Jerusalem after days of clashes between Palestinian protesters and Israeli police at the Al-Aqsa Mosque compound, a flashpoint site sacred to Jews and Muslims. Heavy-handed police tactics at the compound and the threatened eviction of dozens of Palestinian families by Jewish settlers had inflamed tensions.

Since then, Israel has launched hundreds of airstrikes that it says have targeted Hamas’ infrastructure, and Hamas and other militant groups embedded in residential areas have fired some 4,000 rockets at Israeli cities, with hundreds falling short and most of the rest intercepted or landing in open areas.

At least 227 Palestinians have been killed, including 64 children and 38 women, with 1,620 people wounded, according to the Gaza Health Ministry, which does not break the numbers down into fighters and civilians. Hamas and Islamic Jihad say at least 20 of their fighters have been killed, while Israel says the number is at least 130. Some 58,000 Palestinians have fled their homes.

Twelve people in Israel, including a 5-year-old boy, a 16-year-old girl and a soldier, have been killed.

The rockets fired by militants in Lebanon into northern Israel threatened to open up a new front in the fighting. The rocket attack, which drew Israeli artillery fire in response but did not cause any injuries, raised the possibility of dragging Israel into renewed conflict with the powerful Lebanese militant group Hezbollah to its north.

No one claimed responsibility for the attack, and Hezbollah, which fought a monthlong war against Israel in 2006, has stayed out of the fighting for now. The rockets were widely believed to be fired by Palestinian factions based in south Lebanon.

But they cannot operate without Hezbollah’s tacit consent, and the barrage appears to be carefully calibrated to send a political message that the group, which has tens of thousands of missiles, could join the battle at any time. Israel considers Hezbollah to be its most formidable threat and has threatened widespread destruction in Lebanon if war were to erupt.

In Gaza, one of the Israeli airstrikes destroyed the home of an extended family.

Residents surveyed the piles of bricks, concrete and other debris that had once been the home of 40 members of al-Astal family in the southern Gaza town of Khan Younis. They said a warning missile struck the building five minutes before the airstrike, allowing everyone to escape.

Ahmed al-Astal, a university professor, described a scene of panic, with men, women and children racing out of the building.

“We had just gotten down to the street, breathless, when the devastating bombardment came,” he said. “They left nothing but destruction, the children’s cries filling the street. ... This is happening, and there is no one to help us.”

Another strike in nearby Deir al-Balah killed a man, his wife and their 2-year-old daughter, witnesses said. Iyad Salha, a brother of the man who was killed, said the family had just sat down for lunch when the missile hit.

Among those killed Wednesday were a reporter for Hamas-run Al-Aqsa radio and two people who died when warning missiles crashed into their apartment.

The Israeli military said it was striking a militant tunnel network in southern Gaza, with 52 aircraft hitting 40 underground targets.

Military officials, meanwhile, said a mysterious explosion that killed eight members of a Palestinian family on the first day of the fighting was caused by a misfired rocket from Gaza. "This wasn’t an Israeli attack," said Lt. Col. Jonathan Conricus, a military spokesman.

Since the fighting began, Gaza’s infrastructure, already weakened by a 14-year blockade, has rapidly deteriorated. Medical supplies, water and fuel for electricity are running low in the territory, on which Israel and Egypt imposed the blockade after Hamas seized power in 2007.

Israeli attacks have damaged at least 18 hospitals and clinics and destroyed one health facility, the World Health Organization said. Nearly half of all essential drugs have run out.

Among the buildings leveled by Israeli airstrikes was one housing The Associated Press' Gaza office and those of other media outlets.

Netanyahu has alleged that Hamas military intelligence was operating in the building. Secretary of State Antony Blinken said Tuesday that Israel had given the U.S. information about the bombing, without elaborating.

The AP has called for an independent investigation. The news organization's president, Gary Pruitt, has said the AP had no indication Hamas was present in the building.

The fighting, the worst since a 2014 war between Israel and Hamas, has ignited protests around the world and inspired Palestinians in Israel and the occupied territories to call a general strike Tuesday. It was a rare collective action that spanned boundaries central to decades of failed peace efforts. Israel captured the West Bank, east Jerusalem and Gaza in the 1967 Mideast war, territories the Palestinians want for their future state.