President Joe Biden delivered a strong message to Israeli Prime Minister Benjamin Netanyahu on Thursday, emphasizing that future U.S. backing for Israel’s actions in Gaza hinges on the prompt implementation of new measures to safeguard civilians and aid workers.

The approximately 30-minute call between Biden and Netanyahu, occurring just days after Israeli airstrikes resulted in the deaths of seven food aid workers in Gaza, introduced a fresh layer of complexity to the relationship between the two leaders. Biden’s statement represents a notable shift in the stance of his administration, which has traditionally offered unwavering support to Israel’s military operations. For the first time, Biden hinted at a reassessment of U.S. support if Israel does not revise its strategies and facilitate increased humanitarian assistance into Gaza.

While the White House did not specify the potential adjustments to U.S. policy, they could encompass modifications in military sales to Israel and alterations in America’s diplomatic posture on the global stage.

Netanyahu’s office said early Friday that his Security Cabinet has approved a series of “immediate steps” to increase the flow of humanitarian aid into Gaza, including the reopening of a key crossing that was destroyed in the Oct. 7 Hamas attack.

Administration officials had said before that announcement that the U.S. would assess whether the Israeli moves go far enough.

Biden “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.