U.S. Vice President Kamala Harris said the Biden administration was "deeply concerned over reports of civilian casualties in an Israeli strike on a school in Gaza on Saturday.
"Yet again, far too many civilians have been killed," she told reporters after Palestinians claimed some 100 people were killed in the attack.
"We are deeply concerned about reports of civilian casualties in Gaza following a strike by the Israel Defense Forces on a compound that included a school," the White House said in a statement, adding Washington was in touch with Israel to seek more information.
The IDF said it targeted Hamas terrorists, naming at least 19 senior members of the terror group who has used the school as a command center.
Harris repeated calls for a cease-fire in Gaza and said she and U.S. President Joe Biden were working around the clock to reach a deal that would include the release of hostages held by Hamas. "Now is the time," she told a rally in Arizona over the weekend.
Biden who has been pushing for a cease-fire, on Saturday addressed the threat from Iran. After a reporter asked him what message he had for the regime in Tehran that was threatening to attack Israel, Biden said "Don't."
The United States has amassed a military force in the region to respond to an Iranian attack, including the deployment of F-22 stealth weapons to the area.