U.S. Secretary of State Antony Blinken made his strongest criticism of Israel so far, saying there was a “gap” between Israel’s stated intention of protecting civilians and the worsening humanitarian situation in the Gaza Strip.

“It remains imperative that Israel put a premium on civilian protection,” Blinken said on Thursday. His comments came amid mounting condemnation of Israel from the United Nations and other countries over deteriorating conditions in the Palestinian enclave.

The Israel Defense Forces have encircled Khan Younis, the second largest city in the Gaza Strip, and say they are closing in on Hamas leadership. More than 17,000 Palestinians have been killed since Israel launched its bombing campaign in response to Hamas’ Oct. 7 attack.

The United Nations has said its aid program has fallen apart as the war has progressed. It “is no longer a functioning one. It is one of response to opportunity,” Martin Griffiths, the U.N.’s emergency relief coordinator, said Thursday. Degraded roadways have made it nearly impossible for supplies to reach civilians, and only some food and water is being dispersed. “It’s erratic. It’s undependable. And frankly, it’s not sustainable,” he said. Earlier this week, U.N. Secretary-General Antonio Guterres invoked a little-used clause in the organization’s charter to warn the Security Council of an impending catastrophe in Gaza.

Civilians fear that no part of the Gaza Strip is safe. Israel directed civilians living in the north of the enclave to move south when its war against Hamas began, and thousands of people fled to Khan Younis. Now, more than 350,000 people are facing evacuation orders in the city. Some Gazans seeking shelter in Rafah, near the Egyptian border, said their options for safe areas are dwindling: “No place in Gaza is safe and tomorrow they are going to come after us in Rafah,” one father of five told Reuters.

Israel has placed blame for the war’s high civilian toll on Hamas, which it accuses of using human shields and embedding in civilian areas. Hamas has denied the accusation. The IDF said that it believes Yahya Sinwar, the leader of Hamas, is living in Khan Younis. The city is one of the last remaining strongholds for the militant group, and crucial for Hamas: “If Hamas loses Khan Younis, they are done. They may have some enclaves there, but they will lose their centers of gravity,” an Israeli security analyst told The Wall Street Journal this week.