Washington, April 5 (IANS): US President Joe Biden on Thursday told Israeli Prime Minister Benjamin Netanyahu that America's support of Israel's war in Gaza would be determined by the latter announcing and implementing a "series of specific, concrete, and measurable steps to address civilian harm, humanitarian suffering, and the safety of aid workers".

The US President also called for an "immediate ceasefire" to stabilize and improve the humanitarian situation there.

The two leaders spoke on the phone amidst growing outrage around the world over the killing of six aid workers of Spanish American chef and restaurateur Jose Andres's World Central Kitchen.

"President Biden emphasized that the strikes on humanitarian workers and the overall humanitarian situation are unacceptable," said the White House in a readout of the phone call. "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," it added.

He went on to warn Netanyahu that the US policy with respect to Gaza "will be determined by our assessment of Israel's immediate action on these steps".

The American leader also underscored that an "immediate ceasefire is essential to stabilize 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".

Relations between the US and Israel, strong allies in the best and worst of times, have plunged as Israel under Netanyahu is seen to be conducting the war in complete disregard to US' concerns.

Biden is facing mounting pressure at home to use US clout to rein in Israel and in an election year the President can barely afford to lose support, especially in key swing states such as Michigan.

In a tense 30-minute call, the US President went further than ever before in pressing Israel to change its conduct of the war in Gaza.

Asked about what specific changes were demanded by the US, John Kirby, the National Security Council spokesperson, told reporters, "What we want to see are some real changes on the Israeli side and, you know, if we don't see changes from their side there will have to be changes from our side." But he did not specify them.