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Mr Netanyahu vowed to defeat the militant group, which launched surprise attacks on Israel on Saturday morning that killed at least 1,300 people in Israel.
“Hamas is ISIS – and 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.
He added that countries that harbour Hamas members “should be sanctioned”, in an apparent reference to Qatar, where Hamas has an office.
Mr Blinken said the acts carried out by the group “brings to mind the worst of ISIS” and added that there is “overwhelming” bipartisan support in the Congress for Israel's security after the US delivered its first shipments of military support to Israel.
“More is on the way,” Mr Blinken said.
“We have the back of the Israeli people. We have their back today. We’ll have it tomorrow. We will have it every day.”
Israel is already the biggest recipient of US military aid.
The Secretary of State said the purpose of his visit to Tel Aviv would include a focus on US citizens.
“Finally, of course, we’re very focused on our own people, our own citizens. We lost 22 Americans; that number could still go up. It probably will. At the same time, we have a number of Americans who remain unaccounted for,” he said.
“We are working very closely with the government of Israel to determine their whereabouts, and if they have been taken hostage by Hamas, to work to secure their release.”
So far, the US has said that Hamas has captured 25 Americans among at least 100 hostages taken from Israel by the group.
“We continue working with Israel to secure the release of the men, women and elderly taken hostage by Hamas,” Mr Blinken said.
The Secretary of State and his team had met the families of the American missing.
“For families of missing, there's an unrelenting agony of not knowing the fate of their loved ones,” he told reporters at a press conference at the end of his visit. “No one should have to endure what they're going through.”
Mr Blinken was joined on the trip by deputy special presidential envoy for hostage affairs Steve Gillen, who will stay behind to help co-ordinate efforts.
In addition to his meeting with Mr Netanyahu, Mr Blinken also met President Isaac Herzog and the newly formed Security Cabinet.
He toured a donation centre in Tel Aviv, where volunteers greeted him with a Hebrew song.
When he took the podium for the press briefing, Mr Blinken appeared shaken by the conversations he had had and some of the images that he had been shown, which he described as “beyond what anyone would ever want to imagine”.
He likened the attack to what the US experienced on September 11, 2001.
“If you look at the size of Israel's population, this is the size of ten 9/11s,” he said.
Mr Blinken also noted the importance of taking precautions against harming civilians. So far, at least 1,300 people have been killed in Gaza, most of whom were civilians, among them children.
Mr Blinken's visit to Tel Aviv is part of a wider Middle East tour to show Washington's solidarity with Israel after the Hamas attack and to seek to calm the conflict.
“I think the two issues here are the immediate issue of the hostages and working the regional circuit in terms of people with ties to Hamas to get them out, working with especially the Egyptians and Qataris who have those connections,” David Makovsky, director of the Washington Institute for Near East Policy's Project on the Middle East Peace Process, told The National.
Mr Blinken, who was joined on his tour by Barbara Leaf, assistant secretary of state for Near Eastern affairs, and Derek Chollet, State Department counsellor, among others, was to travel to Jordan later on Thursday, where he will meet King Abdullah II and Palestinian President Mahmoud Abbas.
He is also expected to meet regional leaders in Qatar, Egypt, Saudi Arabia and the UAE during his visit to the region.
Meanwhile, Iran's Minister of Foreign Affairs Hossein Amirabdollahian is expected to visit Iraq and Lebanon in a regional tour to discuss the war, Iranian state news agencies reported.