The leaders of the US, Germany, Britain, France and Italy have issued a joint statement condemning the attacks on Israel by Islamist militant group Hamas and expressed their "steadfast and united support" for Israel.
"Over the coming days, we will remain united and coordinated, together as allies, and as common friends of Israel, to ensure Israel is able to defend itself, and to ultimately set the conditions for a peaceful and integrated Middle East region," said the statement by US President Joe Biden, French President Emmanuel Macron, German Chancellor Olaf Scholz, Italian Prime Minister Giorgia Meloni and British Prime Minister Rishi Sunak.
Mr Biden has said that Americans are likely being held hostage by Hamas after its surprise attack on Israel, and that at least 11 US citizens were killed in the assault.
Hamas captured about 150 hostages in its weekend attack on southern Israel from Gaza.
Hamas has threatened to kill the hostages if retaliatory Israeli air strikes continue "targeting" Gaza residents without warning.
The threat came after Israel imposed a total siege on Gaza, cutting off the water supply, which sparked UN fears of an increasingly dire humanitarian situation.
Mr Biden said that Washington, which has moved an aircraft carrier closer to Israel in a show of support, was working with its key ally on efforts to recover the hostages after the "heart-wrenching" attacks.
"Sadly, we now know that at least 11 American citizens were among those killed - many of whom made a second home in Israel," Mr Biden said in a statement after meeting his national security team at the White House.
"While we are still working to confirm, we believe it is likely that American citizens may be among those being held by Hamas," he added.
"I have directed my team to work with their Israeli counterparts on every aspect of the hostage crisis, including sharing intelligence and deploying experts from across the United States government to consult with and advise Israeli counterparts on hostage recovery efforts."
The Israeli-Palestinian conflict's worst escalation in decades has claimed more than 700 lives on the Israeli side, according to the military, while Gaza officials reported at least 400 deaths in Israeli air strikes.
Israeli Prime Minister Benjamin Netanyahu has steeled his shocked nation for what he called a long war ahead, with tens of thousands of Israeli forces already deployed to battle holdout Hamas forces and prepare a possible Gaza ground offensive.
'Ironclad support'
The conflict has stoked fears of a wider conflagration. Lebanon's Iran-backed Hezbollah movement said yesterday it had fired shells and missiles at Israeli positions.
With tensions rising, US Defense Secretary Lloyd Austin said he was sending forces to "bolster regional deterrence efforts" after discussions with Mr Biden.
As well as the USS Gerald R. Ford carrier, this deployment includes a guided missile cruiser and four guided missile destroyers, Austin said in a statement.
"The United States government will be rapidly providing the Israel Defense Forces with additional equipment and resources, including munitions," added Austin, who also spoke with his Israeli counterpart yesterday.
The movement of US ships and planes and the aid to Israel "underscores the United States' ironclad support for the Israel Defense Forces and the Israeli people".
The United States yesterday led calls for condemnation of the Hamas assault on Israel at the United Nations Security Council.
"I expect to hear from the other Council members very strong condemnation of these heinous acts of terrorism committed against the Israeli people and their government," senior US diplomat Robert Wood told reporters.
