United Nations Secretary-General Antonio Guterres said on Friday that a U.S.-backed aid operation in Gaza is “inherently unsafe,” giving a blunt assessment: “It is killing people.”

Israel and the United States want the U.N. to work through the controversial new Gaza Humanitarian Foundation, but the U.N. has refused, questioning its neutrality and accusing the distribution model of militarizing aid and forcing displacement.

Guterres said U.N.-led humanitarian efforts are being “strangled,” aid workers themselves are starving and Israel – as the occupying power - is required to agree to and facilitate aid deliveries into and throughout the Palestinian enclave.

"People are being killed simply trying to feed themselves and their families. The search for food must never be a death sentence,” Guterres told reporters.

"It is time to find the political courage for a ceasefire in Gaza."

Since Israel lifted an 11-week aid blockade on Gaza on May 19, allowing limited U.N. deliveries to resume, the United Nations says more than 400 Palestinians have been killed seeking aid from both the U.N. and GHF operations. A senior U.N. official said on Sunday that the majority of those people were trying to reach GHF sites.

GHF did not immediately respond to a request for comment on Guterres' remarks on Friday. Earlier this week it said: "Bottom-line, our aid is getting securely delivered. Instead of bickering and throwing insults from the sidelines, we would welcome the U.N. and other humanitarian groups to join us and feed the people in Gaza."

GHF uses private U.S. security and logistics firms to operate. It began operations in Gaza on May 26 and said on Friday so far it has given out more than 48 million meals. The U.S. State Department said on Thursday it had approved $30 million in funding for the GHF and called on other countries to also support the group.

Israel and the United States have accused Hamas of stealing aid from the U.N.-led operations, which the militants deny.