US Secretary of State Antony Blinken has said that he raised with Israel the "humanitarian needs" of Gaza while defending the right to retaliate for the deadly Hamas attack.
"We did discuss ways to address the humanitarian needs of people living in Gaza to protect them from harm, while Israel conducts its legitimate security operations to defend itself from terrorism and to try to ensure that this never happens again," Mr Blinken told reporters after talks with Prime Minister Benjamin Netanyahu and other top officials in Tel Aviv.
"We also talked about possibilities for safe passage for civilians who want to leave or get out of the way," he said.
US officials are discussing safe passage both with Israel and Egypt, which also borders the Gaza Strip, ahead of an expected Israeli ground operation.
But Blinken also put the blame on treatment of civilians on Hamas, which unleashed the weekend attack that killed more than 1,200 people in Israel. He gave a new death toll for US citizens, saying at least 25 were confirmed among the dead.
Hamas controls impoverished Gaza, which is blockaded by Israel.
"Hamas continues to use civilians as human shields," Blinken said.
Hamas is "intentionally putting civilians in harm's way to protect themselves, or protect their infrastructure or protect their weapons," he said.
"So that's one of the basic facts that Israel has to deal with."
US will always be 'by your side', Blinken tells Israel
Earlier, Mr Blinken vowed that the US will "always" back Israel but said the Palestinians also had "legitimate aspirations" not represented by Hamas.
"You may be strong enough on your own to defend yourself. But as long as America exists, you will never, ever have to. We will always be there by your side," Mr Blinken said during a meeting with Mr Netanyahu.
US President Joe Biden has vowed unwavering support for Israel and not called for restraint against Hamas, but Mr Blinken hinted at the need for an eventual peace settlement - an idea that has long met resistance from Mr Netanyahu.
"Anyone who wants peace and justice must condemn Hamas' reign of terror. We know Hamas doesn't represent the Palestinian people, or their legitimate aspirations to live with equal measures of security, freedom, justice opportunity and dignity," Mr Blinken said.
Speaking in unusually personal terms, Mr Blinken recalled how his grandfather fled anti-Semitic pogroms in Russia and his stepfather survived Nazi concentration camps.
"I come before you not only as the United States secretary of state but also as a Jew," said Mr Blinken, who has a secular background.
"I also come before you as a husband and father of young children. It's impossible for me to look at the photos of families killed, such as the mother, father and three small children murdered as they sheltered in their home in Kibbutz Nir Oz, and not think of my own children," he said.
Mr Blinken promised that the Biden administration and Congress would work together to meet military requests for Israel, which enjoys wide support across party lines.
"As Israel's defence needs evolve, we will work with Congress to make sure that they're met," he said.
Mr Netanyahu, speaking next to Mr Blinken, voiced appreciation for US support and said that Hamas, which rules Gaza, should be treated like the Islamic State group.
"Just as ISIS was crushed, so too will Hamas be crushed. And Hamas should be treated exactly the way ISIS was treated," Mr Netanyahu said.
NATO urges Israel to be proportionate in response
Earlier, NATO countries told Israel's defence minister they stood by his country after the attack by Hamas, but urged his forces to respond with "proportionality", the alliance said.
Israeli Defence Minister Yoav Gallant briefed his counterparts from the US-led military alliance via videolink as his country's military carries out a bombing campaign after Islamist militants killed over 1,200 people, mostly civilians.
"Secretary General Jens Stoltenberg said that NATO condemned the terrorist attacks in the strongest possible terms, adding: 'Israel does not stand alone'," NATO said in a statement.
"Allies expressed solidarity with Israel, making clear that it has the right to defend itself with proportionality against these unjustifiable acts of terror."
NATO countries "called for Hamas to immediately release all hostages, and for the fullest possible protection of civilians. Allies also made clear that no nation or organisation should seek to take advantage of the situation or to escalate it."
The statement added that "a number of NATO allies made clear that they are providing practical support to Israel as it continues to respond to the situation".
In Gaza, officials have reported more than 1,200 people killed in Israel's uninterrupted campaign of air and artillery strikes, while the UN said more than 338,000 people have been displaced.
For days, black smoke has billowed into the sky above Gaza, where entire city blocks have been razed.
As the war rages on, fears are growing over the fate of at least 150 hostages - mostly Israelis but also foreign and dual nationals - held in Gaza by Hamas.
The militants claimed that four captives died in Israeli strikes and threatened to kill the others if civilian targets were bombed without advance warning from Israel.
Yesterday, Hamas claimed to have released an Israeli woman and her two children who it said had been detained during fighting with Israeli forces, but Israeli television networks rejected the announcement.
Israel has massed forces, tanks and other heavy armour around Gaza after what Mr Netanyahu called "an attack whose savagery... we have not seen since the Holocaust".
To Israel's enemies - states or groups - Mr Biden issued a stern warning not to get involved, saying he "made it clear to the Iranians. Be careful".
Iran has long financially and militarily backed Hamas but insists it had no involvement in Saturday's assault.
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Israel appeared to be readying for a possible ground invasion of Gaza, but also faces the threat of a multi-front war after also coming under rocket attack from militant groups in neighbouring Lebanon and Syria.
"We are waiting to see what our political leadership decides about a potential ground" incursion, army spokesperson Richard Hecht told journalists.
"This has not been decided yet... But we are preparing for a ground manoeuvre if it is decided," he added.
Israel again struck targets in southern Lebanon yesterday, an area controlled by the Iran-backed Hezbollah.
The European Union called for a "humanitarian corridor" to allow civilians to flee the enclave's fifth war in 15 years, while Arab League foreign ministers meeting in Cairo called for aid to be allowed into Gaza "immediately".
