US Vice-President Kamala Harris told Israeli officials they need a “credible and implementable humanitarian plan” before carrying out a military operation in Rafah.
She met with a member of Israel’s wartime Cabinet on Monday, after they travelled to Washington in defiance of Benjamin Netanyahu.
White House officials said Benny Gantz, a centrist political rival of Mr Netanyahu, requested the meeting and that the Democratic administration believed it was important that Ms Harris sit down with the prominent Israeli official despite Mr Netanyahu's objections.
The White House then said in a statement: "They discussed the situation in Rafah and the need for a credible and implementable humanitarian plan prior to contemplating any major military operation there given the risks to civilians.”
President Joe Biden, Harris and other senior administration officials have become increasingly blunt about their dissatisfaction with the mounting death toll in Gaza and the suffering of innocent Palestinians as the war nears the five-month mark.
"The president and I have been aligned and consistent from the very beginning," Ms Harris said in an exchange with reporters shortly before her meeting.
She continued: "Israel has a right to defend itself. Far too many Palestinian civilians, innocent civilians have been killed. We need to get more aid in, we need to get hostages out - and that remains our position."
There are hopes for a hostage deal to free more than 100 people believed still to be in captivity in Gaza following Hamas' October 7 attack on Israel.
She also reiterated the administration's support for a temporary extended ceasefire that would facilitate the release of hostages and allow for a surge of humanitarian assistance throughout Gaza.
Although Ms Gantz holds many of the same hardline views as Mr Netanyahu, he has been seen as more open to compromise on critical issues, including the increased delivery of humanitarian assistance.
The meeting comes after the US on Saturday carried out the first of what are expected to be ongoing airdrops of humanitarian aid into Gaza.
The moment is reflective of the increasingly strained dynamics in the US-Israel relationship, with the US forced to fly badly needed aid past its close ally as it looks to ramp up assistance for desperate civilians in Gaza.
The first airdrop occurred just days after more than 100 Palestinians were killed as they were trying to get food from an Israel-organised convoy.
The White House agreed to the meeting with Mr Gantz even as an official from Netanyahu's nationalist Likud party said Mr Gantz did not have approval from the prime minister for his meetings in Washington.
"We have been dealing with all members of the war Cabinet, including Mr. Gantz," White House national security spokesman John Kirby said, "We see this as a natural outgrowth of those discussions. We're not going to turn away that sort of opportunity."
In addition to his talks with Ms Harris, Mr Gantz met with White House national security adviser Jake Sullivan and National Security Council Middle East coordinator Brett McGurk.
Mr Gantz, just before the start of his White House meetings, told a reporter with Israel's public broadcaster Kan: "There will be an open and honest conversation between two friendly and important countries and partners."
Biden is at Camp David, the presidential retreat just outside Washington, until Tuesday as he prepares to deliver the annual State of the Union address later this week.
Over the weekend, Ms Harris issued an assertive call for a temporary ceasefire deal in Gaza, which administration officials say would halt fighting for at least six weeks.
She also increased pressure on Israel not to impede the aid that workers are trying to get into the region. The White House has been advocating for that framework deal for weeks.
Israel has essentially agreed to the deal, according to a senior Biden administration official, and the White House has emphasised that the onus is on Hamas to come on board.
Biden faces mounting political pressure at home over his administration's handling of the Israeli-Hamas war, which was triggered when militants in Gaza launched an attack, killing 1,200 people and taking about 250 people hostage.
