Jerusalem, Israel - Israeli opposition leader Yair Lapid was headed to Washington Saturday for talks with top officials, his party said, as tensions between the two governments grow over Israel's handling of the Gaza war.

Lapid is expected to meet Secretary of State Antony Blinken, National Security Advisor Jake Sullivan, and other officials, his centrist Yesh Atid party said on X.

President Joe Biden has stood by Israel through six months of devastating fighting, but the killing of seven aid workers in an Israeli air strike earlier this week appears to have brought him the closest yet to a breaking point.

In a tense 30-minute telephone call with Benjamin Netanyahu on Thursday, Biden told the Israeli premier that the strike was "unacceptable" and called for an "immediate ceasefire."

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The two men discussed "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 afterward.

It added that Biden "made clear that US policy with respect to Gaza will be determined by our assessment of Israel's immediate action."

Even before the killing of the aid workers, Washington had voiced concern over Netanyahu's plans for a ground offensive in the far-southern city of Rafah, which is crammed with 1.5 million civilians, many of them displaced from other parts of Gaza.

During his visit, Lapid will also meet with Senate Majority Leader Chuck Schumer, who last month called for a snap election in Israel to give voters a chance to get rid of Netanyahu, whom he described as one of the "major obstacles" to peace.

The Israeli premier dubbed Schumer's comments "totally inappropriate," insisting: "We're not a banana republic."