At least half a million people in the enclave were facing the most severe conditions measured by U.N.-backed international experts: starvation, acute malnutrition and death.

For nearly two years, Israeli and American officials have largely ignored pleas to end policies that limit food aid and other humanitarian supplies for millions of Palestinians.

The United Nations on Friday officially declared a famine in Gaza, the first in the Middle East, warning that over 500,000 residents are now facing...