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US President Joe Biden on Wednesday warned Iran to “be careful” after the Hamas attacks.
His warning came after he spoke to Israeli Prime Minister Benjamin Netanyahu to discuss more US assistance to the Israel military.
“Made it clear to the Iranians: Be careful,” Mr Biden said.
The Pentagon has already sent an aircraft carrier strike group to the Eastern Mediterranean, close to Israel, and is shipping munitions to its ally.
A second carrier is on its way, National Security Council spokesman John Kirby said yesterday.
US officials say the presence of the USS Gerald R Ford and other ships is aimed at deterring Hezbollah in Lebanon and other anti-Israel groups.
Mr Biden was speaking at an event for Jewish-American leaders in the White House.
He and the leaders' organisations launched the country's first national strategy to combat anti-Semitism this year.
“This [Hamas] attack was a campaign of pure cruelty, just hate for cruelty against the Jewish people,” Mr Biden said.
Hamas militants conducted an attack on Israeli soil on Saturday that killed at least 1,200 people, and Israeli forces are now responding with strikes on Gaza that have killed at least 1,100 people.
At least 22 US citizens have been killed.
Mr Biden said he told Mr Netanyahu that Israel should follow “the rules of war”. Israel has already flattened large parts of Gaza and has cut off food and water to the territory's 2.3 million people.
“One thing that I did say, that it is really important, that Israel, [with] all the anger frustration that exist … is that they operate by the rules of war,” he said.
Doug Emhoff, the husband of Vice President Kamala Harris, spoke before introducing Mr Biden.
“I know you're all hurting," he said. "The entire Jewish community is hurting. I'm hurting. We grieve with you. We stand with you."
Mr Emhoff is the first Jewish spouse of a US vice president, and has actively spoken against rising anti-Semitism in the US and globally for the White House.
“There is no place for hate in America, not against Jews, not against Muslims, not against anybody,” Mr Biden later said.
