President Joe Biden told Prime Minister Benjamin Netanyahu on Thursday that continued US support would depend on Israeli actions to protect Gaza civilians, for the first time suggesting conditions on aid as he urged an "immediate ceasefire."

In a phone call after the Israeli killing of seven aid workers – which Israel says was a mistake – Biden urged Netanyahu to "announce and implement a series of specific, concrete and measurable steps to address civilian harm, humanitarian suffering and the safety of aid workers," a White House statement said.

Biden "made clear that US policy with respect to Gaza will be determined by our assessment of Israel's immediate action on these steps," it said.

The US leader told Netanyahu that the strikes on humanitarian workers as well as the humanitarian situation in Gaza, where the United Nations has warned of famine, "are unacceptable."

Biden "underscored that an immediate ceasefire is essential to stabilise and improve the humanitarian situation and protect innocent civilians, and he urged the prime minister to empower his negotiators to conclude a deal without delay to bring the hostages home," the statement said.

Qatar has been leading prolonged talks on a temporary ceasefire that would include the freeing of hostages seized when Hamas carried out the deadliest attack in Israeli history on October 7.

The United States has backed a ceasefire as part of a hostage deal, with hopes it will lead eventually to a long-term settlement.

Biden has for months voiced mounting frustration with Netanyahu, but has also staunchly defended Israel's right to respond to Hamas.

Despite pressure from the left of Biden's Democratic Party, the administration has been racing millions of US dollars worth of military supplies to Israel even while criticising the conduct of the war. (AFP)