President Joe Biden told Israel's Prime Minister Benjamin Netanyahu on Thursday that future U.S. support for Gaza war depends on new steps to protect civilians and aid workers.

Biden and Netanyahu spoke by phone days after Israeli airstrikes killed seven food aid workers in Gaza and added a new layer of complication in the leaders’ increasingly strained relationship.

“He made clear the need for Israel to announce and implement a series of specific, concrete, and measurable steps to address civilian harm, humanitarian suffering, and the safety of aid workers,” the White House said in a statement following the leaders call. “He made clear that U.S. policy with respect to Gaza will be determined by our assessment of Israel’s immediate action on these steps.”

Biden in the call also told Netanyahu that an “immediate ceasefire is essential” and urged Israel to reach deal "without delay," according to the White House.

The leaders conversation comes as the World Central Kitchen, founded by restauranteur José Andrés to provide immediate food relief to disaster-stricken areas, called for an independent investigation into the Israeli strikes that killed the group’s staff members, including an American citizen.

The White House has said the U.S. has no plans to conduct its own investigation even as they called on Israel to do more to prevent the killing and wounding innocent civilians and aid workers as it carries out its operations in Gaza.

The war in Gaza began on Oct. 7, when Hamas-led militants stormed into southern Israel, killing some 1,200 people, mostly civilians, and taking around 250 people hostage.

The Israeli military campaign in Gaza, experts say, sits among the deadliest and most destructive in recent history. Within two months, researchers say, the offensive already had wreaked more destruction than the razing of Syria’s Aleppo between 2012 and 2016, Ukraine’s Mariupol or, proportionally, the Allied bombing of Germany in World War II. It has killed more civilians than the U.S.-led coalition did in its three-year campaign against the Islamic State group.