At least 25 Americans have been killed in the attack by Hamas militants in Israel, Antony Blinken said on Thursday, during a visit to show solidarity with Israel. In a joint statement with the Israeli prime minister, Benjamin Netanyahu, the US secretary of state said Washington was working closely with Israel to secure the release of people taken hostage by Hamas. Netanyahu called Blinken’s visit a “tangible example of America’s unequivocable support of Israel”, and compared Hamas to the Islamic State militant group. “Just as Isis was crushed, Hamas will be crushed,” he said. Blinken reiterated American support. “The message I bring with me is this: you may strong enough on your own to defend yourselves but as long as America exists you will never have to,” he said. Blinken also endorsed Netanyahu’s decision to bring some political opponents into a wartime unity cabinet, and said the US knew Hamas does not represent the true aspirations of the Palestinian people. Blinken will visit Jordan on Friday to meet King Abdullah and Mahmoud Abbas, head of the Palestinian Authority, which operates limited self-rule in the Israeli-occupied West Bank. Abbas, a foe of Hamas, has not directly condemned the attacks on Israel and has blamed the escalation on the neglect of Palestinian grievances. In Gaza, Palestinians lined up outside bakeries and grocery stores after spending the night surrounded by the ruins of pulverized neighborhoods darkened by a near-total power outage. Israel launched new airstrikes and said it was preparing for a possible ground invasion. The war has already claimed at least 2,600 lives on both sides. International aid groups warned that the death toll in Gaza could mount after Israel stopped all deliveries of food, water, fuel and electricity and the enclave’s crossing with Egypt was closed. Egypt said it was trying to allow in aid there. A senior official with the the International Committee of the Red Cross warned that the lack of electricity could cripple hospitals. “As Gaza loses power, hospitals lose power, putting newborns in incubators and elderly patients on oxygen at risk. Kidney dialysis stops, and X-rays can’t be taken,” said Fabrizio Carboni, the ICRC regional director. “Without electricity, hospitals risk turning into morgues.” The United Nations said at least 340,000 Gazans had been made homeless. Nearly 220,000 were sheltering in 92 UN-run schools. At one school, Hanan Al-Attar, 14, said her family had rushed out of their home with nothing but the clothes on their backs as bombs fell. Her uncle went back to fetch some clothes and was killed when the house was hit. “They are bombing the houses on top of civilians, women, and children,” said her grandfather. Lt Col Richard Hecht, an Israeli military spokesman, told reporters forces were “preparing for a ground maneuver” should political leaders order one. A ground offensive in Gaza, whose 2.3 million residents are densely packed into a sliver of land only 25 miles long, would be likely to bring even higher casualties in house-to-house fighting. Israeli reservists, a substantial part of the fighting-aged population in a country with mandatory military service, were flocking from abroad to join the battle. “Everyone is coming. No one is saying no,” said Yonatan Steiner, 24, who flew from New York, where he works for a tech company, to join his old army medical unit. “This is different, this is unprecedented, the rules have changed,” Steiner said, by phone from the border near Lebanon where his regiment is based. Hamas has fired thousands of rockets into Israel since its weekend assault. Militants are holding an estimated 150 people taken hostage. The Israeli energy minister, Israel Katz, said nothing would be allowed into Gaza until the captives were released. “Not a single electricity switch will be flipped on, not a single faucet will be turned on, and not a single fuel truck will enter until the Israeli hostages are returned home,” Katz said.