Israel faced growing U.S. calls to avoid further harm to Palestinian civilians in its fight against Hamas militants in Gaza, as the warring sides on Sunday showed no sign of moving toward reviving their collapsed truce.

As Israeli forces pounded the enclave following the breakdown of a temporary cease-fire, U.S. Vice President Kamala Harris said too many innocent Palestinians had been killed in Gaza, and U.S. Defense Secretary Lloyd Austin deemed it a "moral responsibility" for Israel to protect civilians.

The senior U.S. officials' remarks on Saturday reinforced pressure from Washington for Israel to use more caution as it shifts the focus of its military offensive further south in the besieged Gaza Strip.