She said “there must be an immediate ceasefire for at least the next six weeks”, which would “get the [Israeli] hostages out”.
Earlier, Israel did not attend truce talks in Egypt, saying Hamas was not giving a list of hostages still alive.
Hamas told the BBC it was unable to do so because of the Israeli bombing.
“Practically it is impossible to know who is still alive,” said Dr Basem Naim, a senior Hamas official.
Hamas’s team and mediators from the US and Qatar are understood to be in Egypt’s capital Cairo for the planned negotiations.
Pressure for a ceasefire deal intensified after Thursday’s incident outside Gaza City in the north of the Palestinian enclave where at least 112 people were killed when crowds rushed an aid convoy and Israeli troops opened fire.
Speaking at an event in Alabama on Sunday, Ms Harris said: “What we are seeing every day in Gaza is devastating. We have seen reports of families eating leaves or animal feed, women giving birth to malnourished babies with little or no medical care, and children dying from malnutrition and dehydration.
“As I have said many times, too many innocent Palestinians have been killed.”
The vice-president stressed that “our common humanity compels us to act”, reiterating President Joe Biden’s commitment “to urgently get more life-saving assistance to innocent Palestinians in need”.
On Monday Ms Harris is due to have talks in Washington with Benny Gantz, an influential member of Israel’s war cabinet, to discuss a possible ceasefire deal and increased humanitarian aid for Gaza.
Ms Harris said “there is a deal on the table and as we have said, Hamas needs to agree to that deal. Let’s get a ceasefire. Let’s reunite the hostages with their families, and let’s provide immediate relief to the people of Gaza.”
She also said “the Israeli government must do more to significantly increase the flow of aid. No excuses.”
She was speaking in Selma, Alabama, at an event marking the 1965 attack by state troopers on civil rights demonstrators, known as Bloody Sunday.
The Israeli military launched a large-scale air and ground campaign to destroy Hamas after its gunmen killed about 1,200 people in southern Israel on 7 October and took 253 back to Gaza as hostages.
Gaza’s Hamas-run health ministry says at least 30,410 people, including 21,000 children and women, have been killed in Gaza since then, with some 7,000 missing and 71,700 injured.
Dr Basem Naim, a member of Hamas’s political bureau, told the BBC’s Newshour programme on Sunday that the group was unable to provide Israel with a full list of surviving hostages.
“Practically it is impossible to know who is still alive because of the Israeli bombardment and blockage. They are in different areas with different groups.
“We have asked for a ceasefire to collect that data”, he said, adding: “we cannot accept any preconditions”. He was speaking from Istanbul.
The UK, US and their Western partners consider Iranian-backed Hamas to be a terrorist organisation.
“Hamas is a brutal terrorist organisation that has vowed to repeat October 7th again and again until Israel is annihilated. Hamas has shown no regard for innocent life,” Kamala Harris said, insisting that “Hamas cannot control Gaza”.
