Live updates: Follow the latest news on Israel-Gaza
Instead, the Biden administration said “pauses” to allow aid into Gaza should be considered.
“We do not believe that a ceasefire is the right answer right now,” said National Security Council spokesman John Kirby. “We do not support a ceasefire at this time.”
Washington is “confident” of increasing the number of aid lorries entering Gaza through the Rafah crossing with Egypt to about 100 a day, Mr Kirby said.
“This first phase that we talked to the Israelis about is trying to get it up to about 100 [lorries] a day. We're confident that we can get there in coming days,” he said.
Limited aid has entered Gaza from Egypt under a US-brokered deal, but its volume has fallen far short of the hundreds of lorries a day that aid agencies say are needed.
Israel said it was inspecting cargo to prevent weapons smuggling and guarantee that supplies are not seized by Hamas.
Israel declared war on Palestinian militant group Hamas after it launched an unprecedented wave of attacks inside Israel on October 7, killing more than 1,400 people, mostly civilians, and taking more than 230 people hostage.
More than three weeks on, Israeli Prime Minister Benjamin Netanyahu categorically ruled out a ceasefire in Israel's war against Hamas on Monday, as ground forces pushed into Gaza and freed one hostage.
“Calls for a ceasefire are calls for Israel to surrender to Hamas, to surrender to terrorism,” Mr Netanyahu said after demands from UN agencies for a truce.
“This will not happen,” he told foreign media, vowing his government would “fight until this battle is won”.
The military has released images of Israeli mechanised infantry units grinding through the coastal sands of northern Gaza, while witnesses reported tanks on the outskirts of Gaza city on Monday.
Israel said it hit 600 targets in 24 hours, one of the most intense periods of bombing to date, and that a missing female soldier was rescued from Hamas inside Gaza.
The release of Private Ori Megidish was “secured during a ground operation” inside Gaza the army said, adding she had been reunited with her family in Israel and was “doing well”.
Mr Netanyahu has vowed the war will “eliminate” Hamas, ensuring no possible repeat of the group's attacks.
His government has also promised to free the hostages taken by Hamas and other Palestinian militant groups on October 7.
Israel's campaign has flattened thousands of buildings and Gaza's 2.4 million residents are under near-continuous bombardment, with little access to water, food, fuel and other essentials.
The UN has repeatedly called for a humanitarian truce in the violence, which the Hamas-run Health Ministry in Gaza claims has killed more than 8,000 people, many of them children.
On Monday, the UN agency for Palestinian refugees (UNRWA) said the limited number of aid lorries entering the besieged territory were insufficient to meet the “unprecedented humanitarian needs” there.
“Nearly 70 per cent of those reported killed are children and women,” said UNRWA chief Philippe Lazzarini. “This cannot be collateral damage.”